12.0.1 Photoemission

   Beamline 12.0.1 is a home of highly productive general-purpose

   photoemission experiment (ARPES) which is well-liked by the users;

   Its experimental apparatus has been set up for the efficient

   studies of the electronic structure of almost any solid sample

   The instrument is equipped with the VG-Scienta R3000 electron

   spectrometer and a 6-axis sample goniometer on an open-cycle

   liquid helium cryostat;

   Instrument for the spin-resolved ARPES (VG-Scienta R4000) is

   being set up at Beamline 10.0.1



First ever ARPES data collected

with the Scienta spectrometer

(NSLS, Brookhaven, ca. 1997)



Beamline MANUAL


Alexei Fedorov

Staff Scientist

BL 12.0.1

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September 1, 2015

Beamline (Angle Resolved Photoemission) publications:

  • Total refereed publications (2004-present): 121
  • Phys. Rev. Letters: 29
  • Nature journals: 17
  • Science: 5
  • PNAS: 3
  • PhD theses: 14

Articles in refereed journals:

    1. M. Z. Hasan, Y.-D. Chuang, D. Qian, Y. W. Li, Y. Kong, A. Kuprin, A.V. Fedorov, R. Kimmerling, E. Rotenberg, K. Rossnagel, Z. Hussain, H. Koh, N. S. Rogado, M. L. Foo, and R. J. Cava (2004), Fermi Surface and Quasi-particle Dynamics of Na0.7CoO2 Investigated by Angle-Resolved Photoemission Spectroscopy, Phys. Rev. Lett. 92, 246402.
    2. A. Kuprin, Z. Hasan, Y-D. Chuang, Z. Hussain, D. Qian, M. Foo, R.J. Cava (2005), Angle-Resolved Photoemission Spectroscopy (ARPES) of Na0.7CoO2, International Journal of Modern Physics B 19, 345.
    3. H.-B. Yang, Z.-H. Pan, A.K.P. Sekharan, T. Sato, S. Souma, T. Takahashi, R. Jin, B.C. Sales, D. Mandrus, A.V. Fedorov, Z. Wang, and H. Ding (2005), Fermi Surface Evolution and Luttinger Theorem in NaXCoO2: A Systematic Photoemission Study,Phys. Rev. Lett. 95, 146401. 
    4.  Y.-D. Chuang, J. Pepper, W. McKinney, Z. Hussain, E. Gullikson, P. Batson, D. Qian, and M. Z. Hasan (2005), High-Resolution Soft X-ray Spectrograph at Advanced Light Source, Journal of Physics and Chemistry of Solids 66, 2173.
    5. S.Y. Zhou, G-H. Gweon, C.D. Spataru, J. Graf, D-H. Lee, S. G. Louie, and A. Lanzara (2005), Coexistence of Sharp Quasi-particle Dispersions and Disorder Features in Graphite, Phys. Rev. B 71, 161403(R).
    6. J.D. Koralek, J.F. Douglas, N.C. Plumb, Z. Sun, A.V. Fedorov, M.M. Murnane, H.C. Kapteyn, S.T. Cundiff, Y. Aiura, K. Oka, H. Eisaki, and D.S. Dessau (2006), Laser Based Angle-Resolved Photoemission, the Sudden Approximation, and Quasiparticle-Like Spectral Peaks in Bi2Sr2CaCu2O8+d , Phys. Rev. Lett. 96, 017005.
    7. D. Qian, L. Wray, D. Hsieh, D. Wu, J.L. Luo, N.L. Wang, A. Kuprin, A.V. Fedorov, R.J. Cava, L. Visiu, and M.Z. Hasan (2006), Quasiparticle Dynamics in the Vicinity of Metal-Insulator Phase Transition in NaXCoO2, Phys. Rev. Lett. 96, 046407.
    8. D. Qian, D. Hsieh, L. Wray, Y-D. Chuang, A.V. Fedorov, D. Wu, J.L. Luo, N.L. Wang, L. Viciu, R.J. Cava, and M.Z. Hasan (2006), Low-Lying Quasiparticle States and Hidden Collective Charge Instabilities in Parent Cobabltate Superconductors, Phys. Rev. Lett. 96, 216405.
    9. Z. Sun, Y.-D. Chuang, A.V. Fedorov, J. F. Douglas, D. Reznik, F. Weber, N. Aliouane, D. N. Argyriou, H. Zheng, J. F. Mitchell, T. Kimura, Y. Tokura, A. Revcolevschi, D. S. Dessau (2006), Quasiparticle-like Peaks, Kinks and Electron-Phonon Coupling at the (π,0) Regions in the CMR Oxide La2-2xSr1+2xMn2O7, Phys. Rev. Lett. 97, 056401.
    10. S.Y. Zhou, G-H. Gweon, J. Graf, A.V. Fedorov, C.D. Spataru, R.D. Diehl, Y. Kopelevich, D-H. Lee, Steven G. Louie, and A. Lanzara (2006), First Direct Observation of Dirac Fermions in Graphite, Nature Physics 2, 595.
    11. P. Richard, Z-H. Pan, M. Neupane, A.V. Fedorov, T. Valla, P.D. Johnson, G.D. Gu, W. Ku, Z. Wang, and H. Ding (2006), Nature of the Oxygen Dopant-induced States in High-temperature Bi2Sr2CaCu2O8+x Superconductors: A Photoemission Investigation, Phys. Rev. B 74, 094512.
    12. S.Y. Zhou, G-H. Gweon and A. Lanzara (2006), Low Energy Excitations in Graphite: The Role of Dimensionality and Lattice Defects, Annals of Physics 321, 1730.
    13. A.P. Kuprin, M.Z. Hasan, Y.-D. Chuang, D. Qian, M. Foo, R.J. Cava (2006), Low-lying electronic structure of triangular cobaltite, Journal of Physics and Chemistry of Solids 67, 235.
    14. M.Z. Hasan, D. Qian, M.L. Foo, and R.J. Cava (2006), Are Cobaltates Conventional? An ARPES viewpoint, Annals of Physics 321, 1568.
    15. D. Qian, L. Wray, D. Hsieh, L. Viciu, R.J. Cava, J.L. Luo, D. Wu, N.L. Wang, and M.Z. Hasan (2006), Complete d-Band Dispersion Relation in Sodium Cobabltates,Phys. Rev. Lett. 97, 186405.
    16. E. Rollings, G-H. Gweon, S.Y. Zhou, B.S. Mun, J.L. McChesney, B.S. Hussain, A.V. Fedorov, P.N. First, W.A. de Heer, and A. Lanzara (2006), Synthesis and Characterization of Atomically Thin Graphite Films on a SiliconeCarbide Substrate, J. Physics and Chemistry of Solids 67, 2172.
    17. L. Colakerol, T.D. Veal, H-K. Jeong, L. Plucinski, A. DeMasi, T. Learmonth, P-A. Glans, S. Wang, Y. Zhang, L.F.J. Piper, P.H. Jefferson, A.V. Fedorov, T-C. Chen, T.D. Moustakas, C.F. McConville, and K.E. Smith (2006), Quantized Electron Accumulation States in Indium Nitride studied by Angle-resolved Photoemission Spectroscopy, Phys. Rev. Lett. 97, 237601.
    18. T. Valla, A.V. Fedorov, J. Lee, J.C. Davis, and G.D. Gu (2006), The Ground State of the Pseudogap in Cuprate Superconductors, Science 314, 1914.
    19. Z. Sun, J.F. Douglas, A.V. Fedorov, Y-D. Chuang, H. Zheng, J.F. Mitchell, and D.S. Dessau (2007), A Local Metallic State in Globally Insulating La1.2Sr1.76Mn2O7 well above the Metal-insulator Transition, Nature Physics 3, 248.
    20. John F. Douglas, Hideaki Iwasawa, Zhe Sun, Alexei V. Fedorov, Motoyuki Ishikado, Tomohiko Saitoh, Hiroshi Eisaki, Hiroshi Bando, Takeshi Iwase, Akihiro Ino, Masashi Arita, Kenya Shimada, Hirofumi Namatame, Masaki Taniguchi, Takahiko Masui, Setsuko Tajima, Kazuhiro Fujita, Shin-ichi Uchida, Yoshihiro Aiura, Daniel S. Dessau (2007), Unusual Oxygen Isotope Effects in Cuprates?, Nature 446, E5.
    21. J. Graf, G-H. Gweon, K. McElroy, S.Y. Zhou, C. Jozwiak, E. Rotenberg, A. Bill, T. Sasagawa, H. Eisaki, S. Uchida, H. Takagi, D-H. Lee, and A. Lanzara (2007), Universal High Energy Anomaly in the Angle-resolved Photoemission Spectra of High Temperature Superconductors: Possible Evidence of Spinon and Holon Branches, Phys. Rev. Lett. 98, 067004.
    22. D. Qian, D. Hsieh, L. Wray, E. Morosan, N. L. Wang, Y. Xia, R. J. Cava, and M. Z. Hasan (2007), Emergence of Fermi Pockets in a New Excitonic Charge-Density-Wave Melted Superconductor, Phys. Rev. Lett. 98, 117007.
    23. T. Valla, T.E. Kidd, W-G. Yin, G.D. Gu, P.D. Johnson, Z-H. Pan, and A.V. Fedorov (2007), Hih-energy Kink Observed in the Electron Dispersion of High-temperature Cuprate Superconductors, Phys. Rev. Lett. 98, 167003.
    24. E. E. Krasovskii, K. Rossnagel, A.V. Fedorov, W. Schattke, and L. Kipp (2007), Determination of the Hole Lifetime from Photoemission: Ti 3d States in TiTe2, Phys. Rev. Lett. 98, 217604.
    25. S.Y. Zhou, G.-H. Gweon, A.V. Fedorov, P.N. First, W.A. de Heer, D.-H. Lee, F. Guinea, A.H. Castro Neto, and A. Lanzara (2007), Substrate-induced Bandgap Opening in Epitaxial Graphene, Nature Materials 6, 770.
    26. J. Graf, G-H. Gweon and A. Lanzara (2007), Universal Waterfall-like Feature in the Spectral Function of High Temperature Superconductors, Physica C 460, 194.
    27. A.S. Tremsin, G.V. Lebedev, O.H.W. Siegmund, J.V. Vallerga, J.S. Hull, J.B. McPhate, C. Jozwiak, Y. Chen, J.H. Guo, Z.X. Shen, and Z. Hussain (2007), High Spatial and Temporal Resolution Photon/Electron Counting Detector for Synchrotron Radiation Research, Nucl. Instr. Methods A 580, 853.
    28. S.Y. Zhou, D.A. Siegel, A.V. Fedorov, and A. Lanzara (2007), Departure from the Conical Dispersion in Epitaxial Graphene, Physica E 40, 2642.
    29. H-B Yang, Z Wang and H Ding (2007), Angle-resolved photoemission spectroscopy study on the Fermi surface topology of NaxCoO2, J. Phys.: Condens. Matter 19, 355004.
    30. M.Z. Hasan, D. Qian, M. Foo, R.J. Cava (2007), Low-energy excitations and Fermi surface topology of parent cobaltate superconductor, Physica C 460–462, 186.
    31. S.Y. Zhou, D.A. Siegel, A.V. Fedorov, E. El Gabalay, A.K. Schmid, A.H. Castro-Neto, D-H. Lee, and A. Lanzara (2008), Origin of the Energy Gap in Epitaxial Grapene, Nature Materials 7, 259.
    32. D. Hsieh, D. Qian, L. Wray, Y. Xia, Y. S. Hor, R. J. Cava, and M. Z. Hasan (2008), A topological Dirac insulator in a quantum spin Hall phase, Nature 452, 970.
    33. Y.Xia, D.Qian, D.Hsieh, L.Wray, M.Z.Hasan, L.Viciu, R.J.Cava (2008), The observation of gapped quasi-particles near the metal–insulator transitioninNaxCoO2, Journal of Physics and Chemistry of Solids 69, 2986.
    34. D. Qian, D. Hsieh, L. Wray, Y.-D. Chuang, A. Fedorov, L. Viciu, R. J. Cava, and M. Z. Hasan (2008), Phys. Rev. Lett. 101, 089704.
    35. L. Wray, D. Qian, D. Hsieh, Y. Xia, L. Li,1 J. G. Checkelsky, A. Pasupathy, K. K. Gomes, C. V. Parker, A. V. Fedorov, G. F. Chen, J. L. Luo, A. Yazdani, N. P. Ong, N. L. Wang, and M. Z. Hasan1 (2008), Momentum dependence of superconducting gap, strong-coupling dispersion kink, and tightly bound Cooper pairs in the high-Tc (Sr,Ba)1−x(K,Na)xFe2As2 superconductors (2008), Phys. Rev. B 78, 184508.
    36. D. Qian, D. Hsieh, L. Wray, Y. Xia, R.J. Cava, E. Morosan, M.Z. Hasan (2008), Evolution of low-lying states in a doped CDW superconductor CuxTiSe2 , Physica B 403, 1002.
    37. A. D. Palczewski, T. Kondo, R. Khasanov, N. N. Kolesnikov, A. V. Timonina, E. Rotenberg, T. Ohta, A. Bendounan, Y. Sassa, A. Fedorov, S. Pailhés, A. F. Santander-Syro, J. Chang, M. Shi, J. Mesot, H. M. Fretwell, and A. Kaminski (2008), Origins of large critical temperature variations in single-layer cuprates, Phys. Rev. B 78, 054523.
    38. Y. Xia, D. Qian, D. Hsieh, L. Wray, L. Viciu, R.J. Cava, M.Z. Hasan (2008), Observation of gapped quasi-particles in sodium charge-ordered Na1/2CoO2, Physica B 403, 1007.
    39. D. R. Garcia, C. Jozwiak, C. G. Hwang, A. Fedorov, S. M. Hanrahan, S. D. Wilson, C. R. Rotundu, B. K. Freelon, R. J. Birgeneau, E. Bourret-Courchesne, and A. Lanzara (2008), Core-level and valence-band study using angle-integrated photoemission on LaFeAsO0.9F0.1, Phys. Rev. B 78, 245119.
    40. S. Y. Zhou, D. A. Siegel, A. V. Fedorov, and A. Lanzara (2008), Kohn anomaly and interplay of electron-electron and electron-phonon interactions in epitaxial Graphene, Phys. Rev. B 78, 193404.
    41. D. A. Siegel, S. Y. Zhou, F. El Gabaly, A. V. Fedorov, A. K. Schmidt, and A. Lanzara (2008), Self-doping effects in epitaxially grown graphene, Applied Physics Letters 93, 243119.
    42. S.Y. Zhou, D. A. Siegel, A.V. Fedorov, and A. Lanzara (2008), Metal to Insulator Transition in Epitaxial Graphene Induced by Molecular Doping, Phys. Rev. Lett. 101, 086402.
    43. Chang Liu, G. D. Samolyuk, Y. Lee, Ni Ni, Takeshi Kondo, A. F. Santander-Syro, S. L. Bud’ko, J. L. McChesney, E. Rotenberg, T. Valla, A.V. Fedorov, P. C. Canfield, B. N. Harmon, and A. Kaminski (2008), K-Doping Dependence of the Fermi Surface of the Iron-Arsenic Ba1-xKxFe2As2 Superconductor Using Angle-Resolved Photoemission Spectroscopy, Phys. Rev. Lett. 101, 177005.
    44. Z. Sun, J. F. Douglas, Q. Wang, and D. S. Dessau,A. V. Fedorov, H. Lin, S. Sahrakorpi, B. Barbiellini, R. S. Markiewicz, and A. Bansil, H. Zheng and J. F. Mitchell (2008) Electronic structure of the metallic ground state of La2−2xSr1+2xMn2O7 for x~0.59 and comparison with x=0.36, 0.38 compounds as revealed by angle-resolved photoemission, Phys. Rev. B 78, 075101.
    45. L. F. J. Piper, Leyla Colakerol, P. D. C. King, A. Schleife, J. Zúñiga-Pérez, Per-Anders Glans, Tim Learmonth, A. Fedorov, T. D. Veal, F. Fuchs, V. Muñoz-Sanjosé, F. Bechstedt, C. F. McConville, and Kevin E. Smith (2008), Observation of quantized sub-band states and evidence for surface electron accumulation in CdO from angle-resolved photoemission spectroscopy, Phys. Rev. B 78, 165127.
    46. L. Colakerol, L. F. J. Piper, A. Fedorov, T. C. Chen, T. D. Moustakas and K. E. Smith (2008), Observation of an inverted band structure near the surface of InN, EPL 83, 47003.
    47. S.Y. Zhou, D.A. Siegel, A.V. Fedorov, and A. Lanzara (2008), Departure from the conical dispersion in epitaxial graphene, Physica E 40, 2642.
    48. S. Danzenbächer, D.V. Vyalikh, Yu. Kucherenko, A. Kade, C. Laubschat, N. Caroca-Canales, C. Krellner, C. Geibel, A.V. Fedorov, D. S. Dessau, R. Follath, W. Eberhardt, and S. L. Molodtsov (2009), Hybridization Phenomena in Nearly-Half-Filled f-Shell Electron Systems: Photoemission Study of EuNi2P2, Phys. Rev. Lett. 102, 026403.
    49. D. Hsieh, Y. Xia, L. Wray, D. Qian, A. Pal, J. H. Dil, J. Osterwalder, F. Meier, G. Bihlmayer, C. L. Kane, Y. S. Hor, R. J. Cava, M. Z. Hasan (2009), Observation of Unconventional Quantum Spin Textures in Topological Insulators, Science 323, 919.
    50. Z.-H. Pan, P. Richard, Y.-M. Xu, M. Neupane, P. Bishay, A. V. Fedorov, H. Luo, L. Fang, H.-H. Wen, Z. Wang, and H. Ding, (2009), Evolution of Fermi surface and normal-state gap in the chemically substituted cuprates Bi2Sr2−xBixCuO6+d , Phys. Rev. B 79, 092507.
    51. T. Valla, J. Camacho, Z.-H. Pan, A.V. Fedorov, A. C. Walters, C. A. Howard, and M. Ellerby (2009), Anisotropic Electron-Phonon Coupling and Dynamical Nesting on the Graphene Sheets in Superconducting CaC6 using Angle-Resolved Photoemission Spectroscopy, Phys. Rev. Lett. 102, 107007.
    52. Y. Xia, D. Qian, D. Hsieh, L. Wray, A. Pal, H. Lin, A. Bansil, D. Grauer, Y. S. Hor, R. J. Cava and M. Z. Hasan, (2009), Observation of a large-gap topological-insulator class with a single Dirac cone on the surface, Nature Physics 5, 398.
    53. Y. S. Hor, A. Richardella, P. Roushan, Y. Xia, J. G. Checkelsky, A. Yazdani, M. Z. Hasan, N. P. Ong, and R. J. Cava (2009), p-type Bi2Se3 for topological insulator and low-temperature thermoelectric applications, Phys. Rev. B 79, 195208.
    54. P. Vilmercati, A.V. Fedorov, I. Vobornik, U. Manju, G. Panaccione, A. Goldoni, A. S. Sefat, M. A. McGuire, B. C. Sales, R. Jin, D. Mandrus, D. J. Singh, and N. Mannella (2009), Evidence for three-dimensional Fermi-surface topology of the layered electron-doped iron superconductor Ba(Fe1−xCox)2As2, Phys. Rev. B 79, 220503 (R).
    55. Chang Liu, Takeshi Kondo, A.D. Palczewski, G.D. Samolyuk, Y. Lee, M.E. Tillman, Ni Ni, E.D. Mun, R. Gordon, A.F. Santander-Syro, S.L. Bud’ko, J.L. McChesney, E. Rotenberg, A.V. Fedorov, T. Valla, O. Copie, M.A. Tanatar, C. Martin, B.N. Harmon, P.C. Canfield, R. Prozorov, J. Schmalian, and A. Kaminski (2009), Electronic properties of iron arsenic high temperature superconductors revealed by angle resolved photoemission spectroscopy (ARPES), Physica C: Superconductivity 469, 491.
    56. D. Hsieh, Y. Xia, D. Qian, L. Wray, J. H. Dil, F. Meier, J. Osterwalder, L. Patthey, J. G. Checkelsky, N. P. Ong, A.V. Fedorov, H. Lin, A. Bansil, D. Grauer, Y. S. Hor, R. J. Cava, and M. Z. Hasan (2009), A tunable topological insulator in the spin helical Dirac transport regime, Nature 460, 1101.
    57. Pedram Roushan, Jungpil Seo, Colin V. Parker, Y. S. Hor, D. Hsieh, Dong Qian, Anthony Richardella, M. Z. Hasan, R. J. Cava, and Ali Yazdani (2009), Topological surface states protected from backscattering by chiral spin texture, Nature 460, 1106.
    58. D. Hsieh, Y. Xia, D. Qian, L. Wray, F. Meier, J. H. Dil, J. Osterwalder, L. Patthey, A.V. Fedorov, H. Lin, A. Bansil, D. Grauer, Y. S. Hor, R. J. Cava, and M. Z. Hasan (2009), Observation of Time-Reversal-Protected Single-Dirac-Cone Topological-Insulator States in Bi2Te3 and Sb2Te3, Phys. Rev. Lett. 103, 146401.
    59. M. Sprinkle, D. Siegel, Y. Hu, J. Hicks, A. Tejeda, A. Taleb-Ibrahimi, P. Le Fevre, F. Bertran, S. Vizzini, H. Enriquez, S. Chiang, P. Soukiassian, C. Berger, W. A. de Heer, A. Lanzara, and E. H. Conrad (2009), First Direct Observation of a Nearly Ideal Graphene Band Structure, Phys. Rev. Lett. 103, 226803.
    60. Y. S. Hor, P. Roushan, H. Beidenkopf, J. Seo, D. Qu, J. G. Checkelsky, L. A. Wray, D. Hsieh, Y. Xia, S.-Y. Xu, D. Qian, M. Z. Hasan, N. P. Ong, A. Yazdani, and R. J. Cava (2010), Development of ferromagnetism in the doped topological insulator Bi2−xMnxTe3, Phys. Rev. B 81, 195203.
    61. S. D. Lounis, D. A. Siegel, R. Broesler, C. G. Hwang, E. E. Haller, and A. Lanzara (2010), Resonant photoluminescent charging of epitaxial graphene, Applied Physics Letters 96, 151913.
    62. C. Jozwiak, J. Graf, G. Lebedev, N. Andresen, A. K. Schmid, A. V. Fedorov, F. El Gabaly, W. Wan, A. Lanzara, and Z. Hussain (2010), A high-efficiency spin-resolved photoemission spectrometer combining time-of-flight spectroscopy with exchange-scattering polarimetry, Rev. Sci. Instrum. 81, 053904.
    63. D. A. Siegel, C. G. Hwang, A. V. Fedorov, and A. Lanzara (2010), Quasifreestanding multilayer graphene films on the carbon face of SiC, Phys. Rev. B 81, 241417(R).
    64. D. Qian, · Y. Xia, · L. Wra,y · D. Hsieh, · M.Z. Hasan (2010), Low Energy Electronic Structures in Electron-Doped and Hole-Doped Superconducting (Ba/K)(Fe/Co)2As2, J. Supercond. Nov. Magn. 23, 617.
    65. S.-H. Lee, Guangyong Xu, W. Ku, J. S. Wen, C. C. Lee, N. Katayama, Z. J. Xu, S. Ji, Z. W. Lin, G. D. Gu, H.-B. Yang, P. D. Johnson, Z.-H. Pan, T. Valla, M. Fujita, T. J. Sato, S. Chang, K. Yamada, and J. M. Tranquada (2010), Coupling of spin and orbital excitations in the iron-based superconductor FeSe0.5Te0.5, Phys. Rev. B 81, 220502(R).
    66. A. V. Fedorov (2010), The all-organic route to doping graphene, Physics 3, 46.
    67. L. F. J. Piper, A. R. H. Preston, A. V. Fedorov, S. W. Cho, A. DeMasi, and K. E. Smith (2010), Direct evidence of metallicity at ZnO (0001)-(1x1) surfaces from angle-resolved photoemission spectroscopy, Phys. Rev. B 81, 233305.
    68. L. Andrew Wray, Su-Yang Xu, Yuqi Xia, Yew San Hor, Dong Qian, Alexei V. Fedorov, Hsin Lin, Arun Bansil, Robert J. Cava and M. Zahid Hasan (2010), Observation of topological order in a superconducting doped topological insulator, Nature Physics 6, 855.
    69. D.R Garcia and A. Lanzara (2010), Through a Lattice Darkly - Shedding Light on Electron-Phonon Coupling in the High Tc Cuprates, Advances in Condensed Matter Physics 2010, 807412.
    70. L. Andrew Wray, Su-Yang Xu, Yuqi Xia, David Hsieh, Alexei V. Fedorov, Yew San Hor, Robert J. Cava, Arun Bansil, Hsin Lin and M. Zahid Hasan (2011), A topological insulator surface under strong Coulomb, magnetic and disorder perturbations, Nature Physics 7, 32.
    71. H Ding, K Nakayama, P Richard, S Souma, T Sato, T Takahashi, M Neupane, Y-M Xu, Z-H Pan, A V Fedorov, Z Wang, X Dai, Z Fang, G F Chen, J L Luo and N L Wang (2011), Electronic structure of optimally doped pnictide Ba0.6K0.4Fe2As2: a comprehensive angle-resolved photoemission spectroscopy investigation, Journal of Physics: Condensed Matter 23, 135701.
    72. Z.-H. Pan, J. Camacho, M. H. Upton, A.V. Fedorov, C. A. Howard, M. Ellerby, and T. Valla (2011), Electronic Structure of Superconducting KC8 and Nonsuperconducting LiC6 Graphite Intercalation Compounds: Evidence for a Graphene-Sheet-Driven Superconducting State, Phys. Rev. Lett. 106, 187002.
    73. Su-Yang Xu, Y. Xia, L. A. Wray, S. Jia, F. Meier, J. H. Dil, J. Osterwalder, B. Slomski, A. Bansil, H. Lin, R. J. Cava, M. Z. Hasan (2011), Topological Phase Transition and Texture Inversion in a Tunable Topological Insulator, Science 332, 560.
    74. Liang He, Faxian Xiu, Yong Wang, Alexei V. Fedorov, Guan Huang, Xufeng Kou, Murong Lang, Ward P. Beyermann, Jin Zou, and Kang L. Wang (2011), Epitaxial growth of Bi2Se3 topological insulator thin films on Si (111), Journal of Applied Physics 109, 103702.
    75. X. F. Kou, L. He, F. X. Xiu, M. R. Lang, Z. M. Liao, Y. Wang, A. V. Fedorov, X. X. Yu, J. S. Tang, G. Huang, X. W. Jiang, J. F. Zhu, J. Zou, and K. L. Wang (2011), Epitaxial growth of high mobility Bi2Se3 thin films on CdS, Appl. Phys. Lett. 98, 242102.
    76. Z.-H. Pan, E. Vescovo, A.V. Fedorov, D. Gardner, Y. S. Lee, S. Chu, G. D. Gu, and T. Valla (2011), Electronic Structure of the Topological Insulator Bi2Se3 Using Angle-Resolved Photoemission Spectroscopy: Evidence for a Nearly Full Surface Spin Polarization, Phys. Rev. Lett. 106, 257004.
    77. David A. Siegel, Cheol-Hwan Park, Choongyu Hwang, Jack Deslippea, Alexei V. Fedorov, Steven G. Louiea, and Alessandra Lanzara (2011), Many-body interactions in quasi-freestanding graphene, Proc. Natl. Acad. Sci. 108, 11365.
    78. Z. Sun, Q. Wang, A. V. Fedorov, H. Zheng, J. F. Mitchell, and D. S. Dessau (2011), Localization of electrons due to orbitally ordered bi-stripes in the bilayer manganite La2−2xSr1+2xMn2O7 (x ~ 0.59), Proc. Natl. Acad. Sci. 108, 11799.
    79. M. Neupane, P. Richard, Y.-M. Xu, K. Nakayama, T. Sato, T. Takahashi, A. V. Fedorov, G. Xu, X. Dai, Z. Fang, Z. Wang, G.-F. Chen, N.-L. Wang, H.-H. Wen, and H. Ding (2011), Electron-hole asymmetry in the superconductivity of doped BaFe2As2 seen via the rigid chemical-potential shift in photoemission, Phys. Rev. B 83, 094522.
    80. L. Andrew Wray, Suyang Xu, Yuqi Xia, Dong Qian, Alexei V. Fedorov, Hsin Lin, Arun Bansil, Liang Fu, Yew San Hor, Robert J. Cava, and M. Zahid Hasan (2011), Spin-orbital ground states of superconducting doped topological insulators: A Majorana platform, Phys. Rev. B 83, 224516.
    81. Choongyu Hwang, Cheol-Hwan Park, David A. Siegel, A.V. Fedorov, Steven G. Louie, and Alessandra Lanzara (2011), Direct measurement of quantum phases in graphene via photoemission spectroscopy, Phys. Rev. B 84, 125422.
    82. C. Jozwiak, Y. L. Chen, A. V. Fedorov, J. G. Analytis, C. R. Rotundu, A. K. Schmid, J. D. Denlinger, Y.-D. Chuang, D.-H. Lee, I. R. Fisher, R. J. Birgeneau, Z.-X. Shen, Z. Hussain, and A. Lanzara  (2011), Widespread spin polarization effects in photoemission from topological insulators, Phys. Rev. B 84, 165113.
    83. M.R. Lang, L. He, F.X. Xiu, X.X. Yu, J.S. Tang, Y. Wang, X.F. Kou, W.J. Jiang, A.V. Fedorov, and K.L. Wang (2011), Revelation of topological surface states in Bi2Se3 thin films by in situ Al passivation, ACS Nano 6, 295
    84. Mei-Xiao Wang, Canhua Liu, Jin-Peng Xu, Fang Yang, Lin Miao, Meng-Yu Yao, C. L. Gao, Chenyi Shen, Xucun Ma, X. Chen, Zhu-An Xu, Ying Liu, Shou-Cheng Zhang, Dong Qian, Jin-Feng Jia, Qi-Kun Xue (2012), The coexistence of superconductivity and topological order in the Bi2Se3 thin films, Science 336, 52.
    85. Z.-H. Pan, A.V. Fedorov, C. A. Howard, M. Ellerby, and T. Valla (2012), Phys. Rev. Lett. 108, 149702.
    86. Z.-H. Pan, A.V. Fedorov, D. Gardner, Y.S. Lee, S. Chu, and T. Valla (2012), Measurement of an exceptionally weak electron-phonon coupling on the surface of the topological insulator Bi2Se3 using angle-resolved photoemission spectroscopy, Phys. Rev. Lett. 108, 187001.
    87. Fang Yang, Lin Miao, Z. F. Wang, Meng-Yu Yao, Fengfeng Zhu, Y. R. Song, Mei-Xiao Wang, Jin-Peng Xu, Alexei V. Fedorov, Z. Sun, G. B. Zhang, Canhua Liu, Feng Liu, Dong Qian, C. L. Gao, and Jin-Feng Jia (2012), Spatial and Energy Distribution of Topological Edge States in Single Bi(111) Bilayer, Phys. Rev. Lett. 109, 016801.
    88. M. Neupane, S.-Y. Xu, L. A. Wray, A. Petersen, R. Shankar, N. Alidoust, Chang Liu, A. Fedorov, H. Ji, J. M. Allred, Y. S. Hor, T.-R. Chang, H.-T. Jeng, H. Lin, A. Bansil, R. J. Cava, and M. Z. Hasan (2012), Topological surface states and Dirac point tuning in ternary topological insulators, Phys. Rev. B 85, 2325406.
    89. Paolo Vilmercati, Alexei Fedorov, Federica Bondino, Francesco Offi, Giancarlo Panaccione, Paolo Lacovig, Laura Simonelli, Michael A. McGuire, Athena S. M. Sefat, David Mandrus, Brian C. Sales, Takeshi Egami, Wei Ku, and Norman Mannella  (2012), Itinerant electrons, local moments, and magnetic correlations in the pnictide superconductors CeFeAsO1−xFx and Sr(Fe1−xCox)2As2, Phys. Rev B 85, 220503 (Rapid Commun.)
    90. Lihong Bao, Liang He, Nicholas Meyer, Xufeng Kou, Peng Zhang, Zhigang Chen, Alexei V. Fedorov, Jin Zou, Trevor M. Riedemann, Thomas A. Lograsso, Kang L. Wang, Gary Tuttle, Faxian Xiu (2012), Weak Anti-localization and Quantum Oscillations of Surface States in Topological Insulator Bi2Se2Te,  Scientific Reports 2, 726.
    91. X. F. Kou, W. J. Jiang, M. R. Lang, F. X. Xiu, L. He, Y. Wang, Y. Wang4 X. X. Yu, A. V. Fedorov, P. Zhang, and K. L. Wang (2012), Magnetically doped semiconducting topological insulators, J. Appl. Phys. 112, 063912.
    92. D.A. Siegel, C.Y. Hwang, A.V. Fedorov, A. Lanzara (2012), Electron-phonon coupling and intrinsic bandgap in highly-screened graphene, New Journal of Physics 14, 095006.
    93. Faxian Xiu, Nicholas Meyer, Xufeng Kou, Liang He, Murong Lang, Yong Wang, Xinxin Yu, Alexei V. Fedorov, Jin Zou and Kang L. Wang (2012), Quantum Capacitance in Topological Insulators, Scientific Reports 2, 669.
    94. T. Valla, Huiwen Ji, L. M. Schoop, A. P. Weber, Z.-H. Pan, J. T. Sadowski, E. Vescovo, A. V. Fedorov, A. N. Caruso, Q. D. Gibson, L. Müchler, C. Felser, and R. J. Cava (2012), Phys. Rev. B (Rapid Commun.) 86, 241101(R).
    95. Z. Sun,  Q. Wang J. F. Douglas, Y.-D. Chuang, A. V. Fedorov, E. Rotenberg, H. Lin, S. Sahrakorpi, B. Barbiellini, R. S. Markiewicz, A. Bansil, H. Zheng, J. F. Mitchell, and D. S. Dessau  (2012), Nonmonotonic Fermi surface evolution and its correlation with stripe ordering in bilayer manganites, Phys. Rev. B (Rapid Commun.) 86, 201103(R)
    96. S.-Y. Xu, M. Neupane, C. Liu, D. Zhang, A. Richardella, L.A. Wray, N. Alidoust, M. Leandersson, T. Balasubramanian, J. Sanchez-Barriga, O. Rader, G. Landolt, B. Slomski, J.H. Dil, J. Osterwalder, T.R. Chang, H.T. Jeng, H. Lin, A. Bansil, N. Samarth, and M.Z. Hasan (2012), Hedgehog spin texture and Berry phase tuning in a magnetic topological insulator, Nature Physics 8, 616.
    97. S.-Y. Xu, C. Liu, N. Alidoust, M. Neupane, D. Qian, I. Belopolski, J.D. Denlinger, Y.J. Wang, H. Lin, L.A. Wray, G. Landolt, B. Slomski, J.H. Dil, A. Marcinkova, E. Morosan, Q. Gibson, R. Sankar, F.C. Chou, R.J. Cava, A. Bansil, and M.Z. Hasan (2012), Observation of a topological crystalline insulator phase and topological phase transition in Bb1-xSnxTe, Nature Communications 3, 1192.
    98. N. Xu, T. Qian, P. Richard, Y.-B. Shi, X.-P. Wang, P. Zhang, Y.-B. Huang, Y.-M. Xu, H. Miao, G. Xu, G.-F. Xuan, W.-H. Jiao, Z.-A. Xu, G.-H. Cao, and H. Ding (2012), Effects of Ru substitution on electron correlations and Fermi-surface dimensionality in Ba(Fe1−xRux)2As2, Phys. Rev. B 86, 064505.
    99. T. Valla, Angle-resolved photoemission from cuprates with static stripes (2012), Physica C 481, 66.
    100. Matthew Brahlek, Namrata Bansal, Nikesh Koirala, Su-Yang Xu, Madhab Neupane, Chang Liu, M. Zahid Hasan, and Seongshik Oh (2012), Topological-metal to band-insulator transition in (Bi1-xInx)2Se3 thin films, Phys. Rev. Lett. 109, 186403.
    101. Lin Miao, Z. F. Wang, Wenmei Ming, Meng-Yu Yao, Meixiao Wang, Fang Yang, Y. R. Song, Fengfeng Zhu, Alexei V. Fedorov, Z. Sun, C. L. Gao, Canhua Liu, Qi-Kun Xue, Chao-Xing Liu, Feng Liu, Dong Qian, and Jin-Feng Jia (2013), Quasiparticle dynamics in reshaped helical Dirac cone of topological insulators, Proc. Natl. Acad. Sci. 110, 2758
    102. David A. Siegel, William Regan, Alexei V. Fedorov, A. Zettl, and Alessandra Lanzara (2013), Charge-Carrier Screening in Single-Layer Graphene, Phys. Rev. Lett 110, 146802.
    103. Z.-H. Pan, E. Vescovo, A. V. Fedorov, G. D. Gu, and T. Valla (2013), Persistent coherence and spin polarization of topological surface states on topological insulators, Phys. Rev. B (Rapid Commun.) 88, 041101(R).
    104. Q. D. Gibson, L. M. Schoop, A. P. Weber, Huiwen Ji, S. Nadj-Perge, I. K. Drozdov, H. Beidenkopf, J. T. Sadowski, A. Fedorov, A. Yazdani, T. Valla, and R. J. Cava (2013), Termination-dependent topological surface states of the natural superlattice phase Bi4Se3, Phys. Rev. B (Rapid Commun.) 88, 081108(R)
    105. Eryin Wang, Hao Ding, Alexei V. Fedorov, Wei Yao, Zhi Li, Yan-Feng Lv, Kun Zhao, Li-Guo Zhang, Zhijun Xu, John Schneeloch, Ruidan Zhong, Shuai-Hua Ji, Lili Wang, Ke He, Xucun Ma, Genda Gu, Hong Yao, Qi-Kun Xue, Xi Chen and Shuyun Zhou (2013), Fully gapped topological surface states in Bi2Se3 films induced by a d-wave high-temperature superconductor, Nature Physics 9, 621.
    106. L.A. Wray, S. Xu, M. Neupane, A.V. Fedorov, Y.S. Hor, R.J. Cava, M.Z. Hasan (2013), Chemically Gated Electronic Structure of a Superconducting Doped Topological Insulator System, Journal of Physics: Conference Series 449, 012037.
    107. Z. Sun, Q. Wang, J. F. Douglas, H. Lin, S. Sahrakorpi, B. Barbiellini, R. S. Markiewicz, A. Bansil, A.V. Fedorov, E. Rotenberg, H. Zheng, J. F. Mitchell, and D. S. Dessau (2013), Minority-spin t(2g) states and the degree of spin polarization in ferromagnetic metallic La2-2xSr1+2xMn2O7 (x=0.38), Scientific Reports 3, 3167
    108. P. Zhang, P. Richard, N. Xu, Y.-M. Xu, J. Ma, T. Qian, A.V. Fedorov, J.D. Denlinger, G.D. Gu, and H. Ding (2014), Observation of an electron band above the Fermi level in FeTe0.55Se0.45 from in-situ surface doping, Applied Physics Letters 105, 172601
    109. S. K. Kushwaha, Q. D. Gibson, J. Xiong, I. Pletikosic, A. P. Weber, A. V. Fedorov, N. P. Ong, T. Valla, and R. J. Cava (2014), Comparison of Sn-doped and nonstoichiometric vertical-Bridgman-grown crystals of the topological insulator Bi2Te2Se, Journal of Applied Physics 115, 143708
    110. Choongyu Hwang, Duck Young Kim, D. A. Siegel, Kevin T. Chan, J. Noffsinger, A. V. Fedorov, Marvin L. Cohen, Börje Johansson, J. B. Neaton, and A. Lanzara (2014),Ytterbium-driven strong enhancement of electron-phonon coupling in graphene, Phys. Rev. B 90, 115417
    111. I. Pletikosić, Mazhar N. Ali, A. V. Fedorov, R. J. Cava, and T. Valla (2014), Electronic Structure Basis for the Extraordinary Magnetoresistance in WTe2Phys. Rev. Lett. 113, 216601.
    112. Madhab Neupane, Su-Yang Xu, Raman Sankar, Nasser Alidoust, Guang Bian, Chang Liu, Ilya Belopolski, Tay-Rong Chang, Horng-Tay Jeng, Hsin Lin, Arun Bansil, Fangcheng Chou and M. Zahid Hasan (2014), Observation of a three-dimensional topological Dirac semimetal phase in high-mobility Cd3As2, Nature Communications 5, 3786.
    113. Madhab Neupane, Anthony Richardella, Jaime Sanchez-Barriga, SuYang Xu, Nasser Alidoust, Ilya Belopolski, Chang Liu, Guang Bian, Duming Zhang, Dmitry Marchenko, Andrei Varykhalov, Oliver Rader, Mats Leandersson, Thiagarajan Balasubramanian, Tay-Rong Chang, Horng-Tay Jeng, Susmita Basak, Hsin Lin, Arun Bansil, Nitin Samarth and M. Zahid Hasan (2014), Observation of quantum-tunnelling-modulated spin texture in ultrathin topological insulator
      Bi2Se3 films, Nature Communications 5, 3841.
    114. L. Colakerol, L.F.J. Piper, A. Fedorov , T. Chene, T.D. Moustakas, K.E. Smith (2015), Potassium and ion beam induced electron accumulation in InN, Surface Science 632, 154.
    115. Eryin Wang, Peizhe Tang, Guoliang Wan, Alexei V. Fedorov, Ireneusz Miotkowski, Yong P. Chen, Wenhui Duan, and Shuyun Zhou (2015), Robust Gapless Surface State and Rashba-Splitting Bands upon Surface Deposition of Magnetic Cr on Bi2Se3, Nano Lett. 15, 2031.
    116. P.D. Johnson, H.-B. Yang, J.D. Rameau, G.D. Gu, Z.-H. Pan, T. Valla, M. Weinert, A.V. Fedorov (2015), Spin-Orbit Interactions and the Nematicity Observed in the Fe-Based Superconductors, Phys. Rev. Lett. 114, 167001.
    117. A. P. Weber, Q. D. Gibson, Huiwen Ji, A. N. Caruso, A. V. Fedorov, R. J. Cava, and T. Valla (2015), Gapped Surface States in a Strong-Topological-Insulator Material, Phys. Rev. Lett. 114, 256401.
    118. Madhab Neupane, Su-Yang Xu, Nasser Alidoust, Raman Sankar, Ilya Belopolski, Daniel S. Sanchez, Guang Bian, Chang Liu, Tay-Rong Chang, Horng-Tay Jeng, BaoKai Wang, Guoqing Chang, Hsin Lin, Arun Bansil, Fangcheng Chou, and M. Zahid Hasan (2015), Surface versus bulk Dirac state tuning in a three-dimensional topological Dirac semimetal, Phys. Rev. B 91, 241114(R)
    119. Meng-Yu Yao, Lin Miao, N. L. Wang, J. H. Dil, M. Z. Hasan, D. D. Guan, C. L. Gao, Canhua Liu, Dong Qian, and Jin-feng Jia (2015), Surface states in lightly hole-doped sodium cobaltate Na1−yCoO2, Phys. Rev B 91, 161411(R).
    120. Su-Yang Xu, Madhab Neupane, Ilya Belopolski, Chang Liu, Nasser Alidoust, Guang Bian, Shuang Jia, Gabriel Landolt, Batosz Slomski, J. Hugo Dil, Pavel P. Shibayev, Susmita Basak, Tay-Rong Chang,
      Horng-Tay Jeng, Robert J. Cava, Hsin Lin, Arun Bansil & M. Zahid Hasan (2015), Unconventional transformation of spin Dirac phase
      across a topological quantum phase transition, Nature Communications 6, 6870.
    121. Su-Yang Xu, Ilya Belopolski, Nasser Alidoust, Madhab Neupane,
      Guang Bian, Chenglong Zhang, Raman Sankar, Guoqing Chang, Zhujun Yuan, Chi-Cheng Lee, Shin-Ming Huang, Hao Zheng, Jie Ma, Daniel S. Sanchez, BaoKai Wang, Arun Bansil, Fangcheng Chou, Pavel P. Shibayev, Hsin Lin, Shuang Jia, M. Zahid Hasan (2015), Discovery of a Weyl fermion semimetal and topological Fermi arcs, Science 7, 613.


PhD theses:

  1. Sun, Z., “Angle-Resolved Photoemission Studies on Bi-layer Colossal Magnetoresistive Oxides La2-2xSr2+xMn2O7", doctoral dissertation, University of Colorado at Boulder, Boulder, CO, 2006, Advisor Dan Dessau.
  2. Zhou, S.Y., "Dirac Fermions in Graphene and Graphite : A view from angle-resolved photoemission spectroscopy", doctoral dissertation, Department of Physics, UC Berkeley, Berkeley, CA, USA, 2007, Advisor Alessandra Lanzara.
  3. Pan, Z., “Angle-Resolved Photoemission Studies on High Temperature Superconductor Bi2Sr2CuO6+δ”, doctoral dissertation, Department of Physics, Boston College, Boston, MA, USA, 2008, Advisor Hong Ding.
  4. Graf, J., “Kinks in the angle resolved photoemission and inelastic x-ray spectra of high temperature superconductors”, doctoral dissertation, University of California, Berkeley, CA, USA, 2008, Advisor Alessandra Lanzara.
  5. Jozwiak, C., "A New Spin on Photoemission Spectroscopy", doctoral dissertation, Department of Physics, UC Berkeley, Berkeley, CA, USA, 2008, Advisor Alessandra Lanzara
  6. Colakerol, L., “Electronic Structure and Quantized Surface Electron Accumulation of Narrow Band Gap Semiconductors”, doctoral dissertation, Department of Physics, Boston University, Boston, MA, USA, 2009, Advisor Kevin E. Smith.
  7. Hiesh, D., "Spin-resolved spectroscopic studies of topologically ordered materials" , doctoral dissertation, Department of Physics, Princeton University, Princeton, NJ, USA, 2009, Advisor Zahid M. Hasan.
  8. Xia, YuQi,Photoemission studies of a new topological insulator class: experimental discovery of the Bi2X3 topological insulator class”, doctoral dissertation, Department of Physics, Princeton University, Princeton, NJ, USA, 2010, Advisor Zahid M. Hasan.
  9. Wray, L.A.,Spectroscopic studies of unconventional superconductivity in iron pnictides and doped topological insulators", doctoral dissertation, Department of Physics, Princeton University, Princeton, NJ, USA, 2010, Advisor Zahid M. Hasan.
  10. Neupane, M., “Angle-Resolved Photoemission Studies on Ruthenates and Iron-Based Superconductors”, doctoral dissertation, Department of Physics, Boston College, Boston, MA, USA, 2010, Advisor Hong Ding.
  11. Xu, Y., “Angle-Resolved Photoemission Spectroscopy Study on Hole Doped Iron Pnictides Ba1−xKxFe2As2”, doctoral dissertation, Department of Physics, Boston College, Boston, MA, USA, 2010, Advisor Hong Ding.
  12. Garcia D. R., "Exploring Competing Orders in the High-Tc Cuprate Phase Diagram Using Angle Resolved Photoemission Spectroscopy", doctoral dissertation, Department of Physics, UC Berkeley, Berkeley, CA, USA, 2010, Advisor Alessandra Lanzara.
  13. Siegel D. A., "Electronic Structure of Single-Layer Graphene", doctoral dissertation, Department of Physics, UC Berkeley, Berkeley, CA, USA, 2012, Advisor Alessandra Lanzara.
  14. Weber A. P., "Photoemission Spectroscopy Studies of New Topological Insulator Materials", doctoral dissertation, Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, MO, USA, 2015, Advisor Anthony Caruso.








NaCoO structure














graphene gap



Science image



topological insulator



heavy fermion












 slide         handout







 Eryin Wang (left) and Alexei Fedorov at ALS Beamline 12.0.1 where the induced high-temperature superconductivity in a topological insulator was confirmed. (Source: Roy Kaltschmidt, LBL News Center)



Tales from Beamline 12.0.1


Feb. 2004
Beamline 12.0.1: 10,000 resolving power for the ARPES branch.
Development of the Angle-Resolved Photoemission (ARPES) end-station equipped with the highly efficient electron spectrometer SES-100 brought a new challenge for the beamline staff and the community of scientists interested in performing ARPES experiments. The large gap between the resolving power delivered by the existing variable line space (VLS) plane-grating monochromator (~1200, or deltaE = 50 meV at 60 eV photon energy) and the energy resolution of the SES-100 (~ 5 meV) called for a sharp boost of the resolving power of the monochromator. Although a ten-fold increase of the resolving power on a beamline designed for high-throughput and low-resolution seemed a huge stretch, the yearlong effort shared by the SSG and CXRO staff was a success, and a resolving power of 10,000 has been obtained.  This was achieved with a new VLS grating which, unlike the original 200 lines per millimeter grating, was blazed to operate in a negative diffraction order. The new grating, designed by Eric Gullikson of the CXRO, has both 300 lines and 600 lines per millimeter rulings on a single substrate.  The grating was ruled by T. Tanaka at Hitachi High-Technologies on a gold-coated substrate supplied by the Center. The coating process developed at the CXRO proved to be the ticket to creating a high efficiency grating (see Fig. 1).
 Figure 1. Diffraction efficiency of the new BL12.0.1 VLS gratings measured at a constant deviation angle of 14 degrees at BL6.3.2. Note the excellent agreement between measured and ideal diffraction efficiency.
Figure 2 displays spectrum of double-excitation Rydberg series in He measured using 600 lines/mm grating. The total width of the 2p3d resonance is ~6 meV. This number translates into the resolving power of 10,000.
 Figure 2. Rydberg series of doubly excited Helium measured at BL12.0.1 using the newly installed 600 lines/mm VLS grating. Experimental width of the 2p3d resonance is ~6 meV. This measurement demonstrates the resolving power of 10,000.
May 2005
The scientific program at the ARPES branch is mainly focusing on the studies of strongly correlated materials, including high-temperature superconductors, colossal magneto-resistance compounds (CMR), and exotic superconductors (e.g. doped cobalt oxides). A UC Berkeley group led by A. Lanzara studied the electronic structure of carbon nano-tubes and diluted magnetic semiconductors. Tuning to the wishes of many users, we have designed and built a new sample manipulator capable of three rotational degrees of freedom. It is coupled to the liquid helium cryostat which can cool the sample down to 13 K.  Another important upgrade is a sample load lock chamber allowing simultaneous loading and storage of up to six samples. Besides the sample garage, this load lock chamber is equipped with a compact e-beam heater and thermocouple. Hence, samples can be annealed at temperatures up to 3000° C. Since many of the compounds studied at the ARPES end-station have a limited lifetime in the vacuum chamber and are generally not available in big quantities, great time was spent improving the vacuum conditions. For example, CMR material LaSrMnO (which is probably the most sensitive sample) does not show signs of aging during the typical eight hour period required for its complete measurement. A useful feature of the new manipulator is the “sample garage” with two extra parking spaces that may be used to keep multiple samples inside the main chamber at once and allow for one sample to be studied without bringing another out of UHV conditions.
June 2006
Our initial plan to install the high order light supressing filters during the two-bunch mode in August has been abruptly altered when the vacuum leak in the bellow of the rotary feed-through mounted on the sample manipulator has opened about three weeks ago. Since venting of the main chamber was unavoidable, we have decided to vent a mirror tank too and to install the filters. Four different filters (Mg, Al, Si, and B) have been installed. Al and B filters have been supplied by the LeBow Corporation and CXRO has made a Si filter. Obtaining a good Mg filter was particularly challenging due to the reactive nature of this material. This filter was manufactured by Luxel Inc. which had to go through a several attempts to sandwich thin Mg foil between the protective layers of aluminum. The final product was a Mg film (0.2 micron) sandwiched between 150-Angstrom thick aluminum layers. All filters have been attached to the rectangular frames with 1-inch wide circular apertures.
Figure 1 displays transmission of Mg filter. Transmission was measured at beamline 6.3.2 (CXRO`s EUV testing and calibration beamline) by Eric Gullikson
Figure 2 shows angle-resolved photoemission spectra of Bi2Sr2CaCu2O8 (well-known high critical temperature superconductor) excited by 28 eV photons without (A) and with (B) Mg filter. Dramatic reduction of the parasitic background is obvious:
Aug. 2006
Recently the photoemission community became excited about experiments performed at low photon energies as they offer considerable enhancement of the sensitivity to the bulk of the sample: The low photon energy translates into the photoelectrons with the very low kinetic energies and, consequently, an increased mean free path. Currently BL12.0.1 cannot support such photoemission experiments:  Although it is possible to get photons at as low as ~27 eV, the photon flux drops dramatically making many experiments impractical. About a year ago, we have decided to extend the useful range to ~20 eV and to purchase additional diffraction grating with efficiency optimized for low energies. Eric Gullikson (CXRO) has designed the grating, while funds for purchasing it from the HITACHI High Technologies were provided by Daniel Dessau (U. Colorado, Boulder). The grating was delivered a few weeks ago. The figure below compares its calculated and measured efficiencies (efficiency was measured by Eric Gullikson at BL6.3.2). The agreement is excellent. We are very satisfied with the quality of the grating and we look forward to installing it at the beamline sometime during the fall shutdown.
May 2007
Some years ago, the “National Electrostatic Corporation” (Middleton, Wisconsin) has manufactured the photon beam position monitorts for the Atomic and Molecular Science branches of BL10.0.1 The devise consists of the helically shaped wire constantly spinning inside the photon beam pipe. When photon beam hits the spinning wire it generates photoelectrons producing the electron current between the wire and the surrounding collector. If photocurrent is displayed versus the angle of rotation, it usually shows two peaks representing beam profiles along two orthogonal directions X and Y. The devise proved to be a very valuable tool for aligning photon beams. However, the model installed at BL10 utilized lubricated ball bearings. Lubrication ensured a good lifetime of a constantly spinning device. On the other hand, it prohibited use of the Beam Position Monitors (BPM`s) at other beamlines where UHV compatibility outlaws any lubricants. In attempt to get an UHV compatible BPM, the ALS has ordered custom units equipped with the dichronite ball bearings using no lubricants. These BPM`s delivered about a year ago had a very short lifetime due to the failure of non-lubricated (UHV-friendly) ball bearings. On overage, they run for less than a week.  To fix the problem at BL12 we have decided to use commercial magnetically coupled rotary feed-through (we bought mini-CF rotary manufactured by the "UHV-Design", Lewes, England) driven by the stepper motor with angular encoder. Hence, we threw away magnetically coupled feed-through (and original ball bearings) which was an integral part of the BPM as well as an asynchronous motor driving it. The stepper motor with encoder gave as a flexibility of running BPM at desired speeds, e.g. high speed for the fast feedback or low speed for the higher sensitivity. The latter option should be beneficial for the bending magnet beamlines with low photon flux. It also increases the lifetime of the BPM. Encoder has eliminated the original BPM controller with rather complicated electric circuitry providing the reference signal for calculating angular position of the spinning helical wire. Use of the commercial rotary feed-through ensures easy and quick treatment of the future failures of the bearings. Signals from the BPM (photocurrent) and encoder (angular position) are feed into the beamline software which displays beam positions (and profiles) along two orthogonal directions.
Apr. 2009
Recently we have conducted photoemission experiment with the sample which gave us a chance to learn about the lateral stability of sample and beam position at the photoemission branch of BL12.0.1. The sample was a single-crystalline flake of graphite measuring about 20 or 40 microns. While registering photon beam on this sample was a relatively easy task since angle-resolved photoemission from graphite gives a unique linear dispersion (see Figure 1), keeping this position over a long period of time proved to be difficult.
During the first hour we had to move sample along the vertical direction by ~10 microns every five minutes as sample or beam position were slowly drifting. Figure 2 shows “optimal” sample position versus time.
The plot suggests that it took about 3.5 hours to settle all the drifts. The drift was only noticeable for the vertical position. Neither X or Y positions had to be adjusted. This brings up two possible origins of the drift:
Drift of the sample position: Sample was cooled down to the liquid helium temperature. The cool down of the sample to the base temperature took only 30 minutes. However, it is possible that it took a way longer for the vertical support structure of the sample holder to reach equilibrium temperature. Naturally, the slow cool down of the support structure shall result in the drift of the vertical position of the sample.
Drift of the beam position: The vertical refocusing mirror of the photoemission beamline does not see the photon beam until it is directed into this branch. Hence, it must take some time to stabilize the temperature of this mirror. In essence, in the independent measurement performed some time ago we have noticed the slight drift of the beam position caused by the vertical mirror. This drift went away after ~30 minutes.
At the moment we believe that the major source of the drift observed in the present experiment is the slow cool down of the sample manipulator. This shall be investigated in the future after we attach temperature sensors to the various spots on the sample manipulator.
The good news is that for the experiments which require great stability of the sample position we could guarantee stability of ~ 10 microns (or better) provided the sample has been cooled down for at least three hours. Another positive outcome of the present study is an estimation of the size of the beam spot in the vertical direction. We think it shall be close to 40 microns. Horizontal size must be greater simply because sample is never normal to the beam
Sept. 2010
It looks as at BL12 a black hole has developed which traps everyone interested in topological insulators. Several research groups have plunged in and managed to send out important messages. Through recent publication in “Nature Physics” (advanced online publication, September 19, 2010; http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys1762.html) group of Prof. Zahid Hasan (Princeton University) has communicated studies of Bi2Se3 doped with Cu. This sample is the first known example of three-dimensional topological insulator which is also a superconductor in the bulk. It has a transition temperature of ~3.8 Kelvin. Superconductivity develops in the bulk of the sample while its top layer is characterized by the presence of the topological surface state. Now we dream of future measurements on these and similar samples when improved sample manipulator would be capable of reaching such low temperatures.
Another flurry of activity on topological insulators took place during the two-bunch run when fully commissioned and configured to work with cleavable samples TOF spectrometer was brought to the beamline by the group of Prof. Alessandra Lanzara at UC Berkeley. For two weeks it has occupied place originally claimed by the new end-station for angle resolved photoemission. The run has produced much awaited data on spin structure of topological surface states. Experiments were conducted in collaboration with the ALS staff and members of the group lead by Prof. Z.-X. Shen in Stanford University.
BL12 is bound to see more activity on topological insulators since it is receiving ever increasing number of new proposals wishing to study these materials.
Studies of more conventional samples also resulted in publications. Prof. Kevin Smith and his group (Boston University) reported their work on surfaces of ZnO (Phys. Rev. B 81, 233305).
Lastly, a sole fact of “being around for a long time” has helped Alexei to score a publication when he was invited by the editors of Phys. Rev. B to write a viewpoint for “Physics” (Physics 3, 46)
Oct. 2010
The addition of spin resolution to photoemission was an important step in experimental studies of band structure in magnetic materials. The popularity of the technique reached its apogee a couple of decades ago. However, it’s wide spread use was somewhat prohibited by the pains caused by low count rates and moderate resolutions. Not surprisingly, most activities these days are confined to synchrotron light sources offering high photon fluxes. Until now, the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory has not hosted a dedicated facility for spin resolved photoemission for many years while regular angle resolved photoemission (ARPES) is present at four beamlines.  The situation is about to change soon as the Scientific Support Group at the ALS has decided to supplement its ARPES facility operating at BL 12.0.1 since ca. 2002 with a station dedicated for spin resolved ARPES. To a great degree this development was motivated by the recent experiments on the surface electronic structure in topological insulators /M.Z. Hasan and C.L. Kane, Topological Insulators, arXiv:1002.3895v1, to be published in Rev. Mod. Physics (2010)/, the majority of which was conducted at this beamline. Electrons on the surfaces of topological insulators are confined into surface states that maintain specific orientation of their spins. The instrument planned for the ALS will be based on the R4000 spectrometer supplied by VG-Scienta, and spin detection will be achieved by the use of a Mott detector and a low energy detector based on exchange scattering. If work proceeds according to schedule, the spin resolved photoemission facility will be commissioned by the end of 2011.
Dec. 2010
Eligibility of the “publish-or-perish” approach to measuring productivity in science is a popular discussion topic in many scientific journals, with many voting for its abolishment, for it creates unhealthy pressures. The truth, however, is that everyone is usually impressed by the gleaming publication records of celebrity scientists. Scientific facilities are not different in this respect and the Advanced Light Source can proudly report that during the period covered by the upcoming review by the Department of Energy, which is from 2008 to 2011, it has done exceptionally well supporting research relying on the technique of photoelectron spectroscopy. Its major photoemission beamlines (three ARPES beamlines: 7.0.1, 10.0.1 and 12.01, and two high-pressure XPS beamlines: 9.3.2 and 11.0.2) have contributed to 45 papers published in: “Nature”, “Science” and “Physical Review Letters” which are recognized as “premier journals”. Of these 45 papers, 24 were published in PRL, 17 were printed in Nature journals (“Nature”, “Nature Physics” and “Nature Materials”) and 4 have appeared in “Science”. To help to appreciate this achievement we should mention that “paper count” of other synchrotrons renowned for their research in photoemission is considerably lower. BESSY is next to the ALS with 29 papers, while SSRL, SRC, Swiss Light Source and Hiroshima Radiation Center can each claim about 20 papers. Interestingly, 45 high profile publications of the ALS are split almost equally between its three ARPES beamlines (7, 10 and 12). Statistics is a captive field. Someone might go farther and calculate amount of beam-time shifts, manpower, dollars, sleepless nights, etc. which have been spent for every publication.
Feb. 2011
We are steadily moving towards establishing a permanent photoemission facility capable of resolving spin polarization of the photo-emitted electrons. It will support spectroscopic technique, which is commonly known as spin-resolved photoemission. Development of the new instrument will be conducted in phases: “Phase one” will result in the instrument based on the popular “Mott spin detector” (device which measures spin of the electrons) coupled to the hemispherical electron energy analyzer, while “Phase two” will bring spin detector based on the novel and yet unexplored techniques. Given our accumulated experience in the development of the new instrumentation and the record of excellence in supporting photoemission research at the ALS, we are looking forward to setting up an instrument, which will outperform all existing facilities for spin resolved photoemission. First essential parts of the new facility (electron analyzer and Mott detector) have been recently delivered to the ALS and work on shaping the new end-station has already began.
Mar. 2011
This year at least one invited and nine regular talks that were given by the users of BL12 at the annual March meeting of the American Physical Society (Dallas, March 21-25) contained photoemission data taken at the ALS. The talks were mainly devoted to the studies of topological insulators and graphene, which remain the hottest subjects of the condensed matter physics. Graphene has already yielded the Nobel Prize. Luckily, topological insulators will share same degree of recognition as they might constitute devices transmitting signals without losses (they are not yet “room-temperature superconductors” though, but we shall see). Hence, photoemission at beamline 12 is still at the forefront of the photoemission research. Planned addition of the spectrometer for spin-resolved photoemission will further strengthen its leadership.
Apr. 2011
Users of photoemission instrument at BL12.0.1 have a new paper which just has appeared in Science (http://www.sciencemag.org/content/332/6029/560.abstract) and Science Express. Predictably, it reports latest discoveries made in topological insulators by the Princeton group of Prof. Z. Hasan and their collaborators.
The paper on superconductivity in LiC6 and KC8 has been accepted for publication in Phys. Rev. Lett. This study is the product of collaboration including Brookhaven National Lab., ALS, Argonne National Lab and University College London.
New users came from UCLA with samples of topological insulators grown by molecular beam epitaxy. Their research aims at producing working electrical device based on the unique physics of these materials. This work is promoted by the serious interest from big manufactures (Intel, etc.).
May 2011
A few good and not so good things happened at BL12 during this month. We start with the good news:
Crew of the photoemission branch of BL12 has doubled after Peng Zhang, a graduate student from the Institute of Physics, Chinese Academy of Science, has joined on May 2. Peng comes from the group of Prof. Hong Din. He will be stationed at BL12.0.1 for one year.
More good news: Paper on the superconductivity in KC6 has appeared in Phys. Rev. Lett. (http://prl.aps.org/abstract/PRL/v106/i18/e187002). Paper on the epitaxial grows of high quality films of topological insulator Bi2Se3 has been published in Journal of Applied Physics (http://m.jap.aip.org/resource/1/japiau/v109/i10/p103702_s1). Several interesting papers have been accepted for publication. We will write about them after they come out from the print.
Bad news: We noticed that electron lens in our new VG-Scienta spectrometer had a slight tilt. Close inspection of the lens concluded that it became loose. We had to remove spectrometer from the vacuum chamber and investigate the problem. We found that two out of six ceramic rings holding the lens elements together were broken. We believe they broke during the routine bake of the chamber and that the cause of the problem is the faulty design of the lens assembly which did not properly consider different thermal expansions of the materials used in the lens. Our findings will be communicated to the manufacturer. In a mean time the good solution has been found and implemented. Naturally, we were not left alone to face all the problems. Hence, we are thankful to the following staff members who gave us a helpful hand: Monroe Thomas, Derrick Crofoot, John Pepper, Kyle McCombs, and Andrew Mei.
June 2011
This month three interesting papers have been added to the publication list of the photoemission branch of BL12:
Study of spin polarization of the surface states in the topological insulator is published in Phys. Rev. Lett.:http://prl.aps.org/abstract/PRL/v106/i25/e257004. This paper is the outcome of the collaboration between Brookhaven National Lab, MIT and ALS/LBNL.
Paper on the many-body interactions in the free-standing graphene is appearing in June 27th issue of the Proceedings of the National Academy of Sciences (PNAS): http://www.pnas.org/content/early/2011/06/20/1100242108.abstract. It summarizes systematic photoemission work conducted at BL12 over a few years by the UC Berkeley group of A. Lanzara.
Paper on the electronic structure of manganites is scheduled to appear in the same issue of PNAS. The paper is the result of the long lasting collaboration between University of Colorado Boulder, Argonne National Lab and ALS/LBNL.
July 2011
Two papers based on the angle-resolved photoemission (ARPES) data taken at the beamline 12.0.1 and 10.0.1 appear on the Proceedings of the National Academy of Sciences (PNAS).
The paper lead by Colorado group, in collaboration with LBNL and ANL, investigates colossal magneto-resistance material (La, Sr)2Mn2O7. They find a strong variation in electronic structure at the metal-insulator transition boundary accompanies the melting of bi-stripes. The presence of localized electrons even below the critical temperature suggests that the melting bi-stripes exist in a disordered or fluctuating state.
An UC-LBNL collaboration produced a paper  regarding the electronic structure of quasi-freestanding graphene at the charge neutrality point, i.e., when the chemical potential coincides with the Dirac energy. They find many body interactions in monolayer, graphene changes strongly as the doping level reaches the charge neutrality point. The electron-electron interaction results in unique renormalization, much different from ordinary metals, while the electron-phonon interaction diminishes.
Both articles are also featured in LBNL News Center: http://newscenter.lbl.gov/feature-stories/2011/07/14/manganite-stripes/ & http://newscenter.lbl.gov/feature-stories/2011/07/14/graphene-secrets/.
Oct. 2011
Regular multi-bunch beamtime during the months of September and October were divided between users from UCLA, U. Colorado Boulder, Princeton University, Brookhaven National Lab, and UC Berkeley. Beamtime during two weeks of the two-bunch mode was solely taken by C. Jozwiak (UC Berkeley and ALS) for experiments on spin-resolved photoemission. A paper reporting observation of quantum phases in graphene was published by the users from UC Berkeley (Choongyu Hwang et al, http://prb.aps.org/abstract/PRB/v84/i12/e125422). Alexei has expanded his community services to Europe by joining the proposals study panel at Elettra synchrotron in Italy.
Nov. 2011
A disaster occurred at the photoemission branch of BL12 when a user wished to study a single crystal of antimony (Sb) by ARPES and wanted to clean the surface of the sample “in situ” using tools of the sample preparation/loading chamber attached to the main photoemission facility. Alexei--overwhelmed with a dense sequence of experiments that demanded various methods of preparation of very different samples--had no time to thoroughly investigate the accumulated knowledge on how to deal with antimony and had advised the user to check the literature. The user had found a reference(s) reporting preparation of atomically clean antimony via cycles of sputtering and annealing. Before starting the first cycle of sample preparation, Alexei decided to degas the sample and its holder by heating them to about 200C which, according to the user, was just a fraction of annealing temperature reported in the reference he had found. Disaster occurred after approximately 20 minutes of degassing when the antimony sample started to sublimate, covering inside of the preparation chamber. Since antimony is a toxic material, the entire chamber and its guts had to be disassembled and cleaned in Bldg. 77 leaving Alexei with only few days to put everything back together for the next experiment scheduled for a user coming from China. Luckily, after a great deal of hard work, he was able to meet the deadline, hence enabling the next scheduled experiment (which yielded a very impressive set of data!). As to the ARPES study of antimony, it actually has ended up with some success since the user had another sample which Alexei was able to clean after developing his own recipe of sample preparation. The moral: regardless of your workload and circumstances, always check what users want to do in the chamber and perform the literature search yourself even if the users come from a credible group/university. Since this user also conducts experiments at beamlines 4 (Merlin) and 10 (HERS), Alexei has promptly shared his experience and advised colleagues on how to deal with antimony samples (and the user). Doug Taube helped with the clean-up, and John Pepper (and his team) helped with the mechanical repairs.
Mar. 2012
Beamtime during two weeks of the two-bunch run in March has been reserved for the photoemission experiments conducted by UC Berkeley group of A. Lanzara. Their instrument (spin-resolved photoemission based on Time-of-Flight spectrometer) was brought to the beamline and connected downstream of two permanent photoemission end-stations. Recently we have installed and commissioned a new horizontal focusing mirror, which now lets us deliver focused beam to this roll-up chamber rather easily. The old mirror did not focus beam that far away from the main photoemission chamber and we had no option but to swap our second permanent end-station with the roll-up chamber. This was a big and very time consuming job.  Installation of the roll-up, its alignment and beam delivery went very smoothly.
Collaboration between scientists from Shanghai Jiao Tong University (China), Institute of Physics, Chinese Academy of Sciences, Pennsylvania State University, Stanford University, and Tsinghua University in Beijing has used photoemission beamline 12 to get one step closer to experimental discovery of Majorana fermions. Collaboration has reported results in Science Express (on-line publication of selected Science papers in advance of print):  http://www.sciencemag.org/content/early/2012/03/14/science.1216466
Apr. 2012
The ALS experimental floor is densely covered with shiny stainless chambers. Curiously, most of them are empty. Seriously, the majority of the ALS experiments shall be conducted under vacuum since even a small contamination of the sample by the residual atoms and molecules can surely spoil it and ruin the experiment. Recently in the photoemission chamber of BL12.0.1, we have witnessed vacuum, which is only rarely achieved on Earth: 1.7x10E-11 Torr. Getting such vacuum was not easy. We had to scrupulously inspect every inch of the chamber searching for tiny leaks. According to NASA, similar vacuum conditions exist at the surface of the Moon (Mars has only 5 Torr), while vacuum around the International Space Station is about 1E-9 Torr. Vacuum of the outer space has inspired proposals to grow clean materials in the space. In essence, a few MBE samples have been grown during several Space Shuttle missions. It would be interesting to compare the cost of growing samples in space to the cost of making them on Earth inside our chamber or any other chamber with similar vacuum. All joking aside, the users have appreciated our effort, after recognizing that their samples last longer and survive numerous cycles of cool-downs and warm-ups.
May 2012
In May the photoemission branch of BL12 has hosted users from Institute of Physics, Chinese Academy of Sciences and from Shanghai Jiao Tong University. Photoemission apparatus at BL12 became an important experimental facility used by the international synergies of universities and government laboratories for studying electronic structure of novel materials. On May 3rd Physical Review Letters published a paper reporting study of the electron-phonon coupling in topological insulators (http://prl.aps.org/abstract/PRL/v108/i18/e187001). The study was conducted at the beamline by the beamline staff and collaborators from BNL and MIT. Story is featured by the LBNL Communications and Media Relations at http://newscenter.lbl.gov/feature-stories/2012/05/14/topological-insulators/
Oct. 2012
Over the summer we have made a few significant steps towards establishing facility for spin-resolved photoemission at the ALS. Alexei has designed a couple of new chambers which will house electron spectrometer and tools for sample preparation. By the time this note was done been written the chambers were already on board of the UPS truck heading from NorCal production facility in Yreka to LBNL. Amuneal Manufacturing Company of Philadelphia has been charged with the design and production of the magnetic shields for the analysis chamber. As usual, John Pepper was around to help with the cool design ideas. It is important to remember than the only operational beamline for spin-resolved photoemission in the country is stationed at the NSLS (Brookhaven) which will be turned off soon. Hence, here at the ALS we ought to maintain a steady progress and commission our facility soon.
Nov. 2012
This was a good and calm month with only one emergency involving the cracked bellow. Chamber was vented and the bellow was removed. Users were not affected; end-station was back on-line almost instantly. Below is the summary of recent publications (topological insulators still dominate):
Fang Yang, et al., Spatial and Energy Distribution of Topological Edge States in Single Bi(111) Bilayer, Phys. Rev. Lett. 109, 016801
M. Neupane et al., Topological surface states and Dirac point tuning in ternary topological insulators, Phys. Rev. B 85, 2325406
Paolo Vilmercati, et al., Itinerant electrons, local moments, and magnetic correlations in the pnictide superconductors CeFeAsO1−xFx and Sr(Fe1−xCox)2As2, Phys. Rev B 85, 220503 (Rapid Commun.)
Lihong Bao, et al., Weak Anti-localization and Quantum Oscillations of Surface States in Topological Insulator Bi2Se2Te, Scientific Reports 2, 726
X. F. Kou et al., Magnetically doped semiconducting topological insulators, J. Appl. Phys. 112, 063912
D.A. Siegel, et al., Electron-phonon coupling and intrinsic bandgap in highly-screened graphene, New Journal of Physics 14, 095006
Faxian Xiu et al., Quantum Capacitance in Topological Insulators, Scientific Reports 2, 669
Mar. 2013
Although it might seem to the uninitiated observer that the daily routines of the beamline scientists include working on bolts and nuts or hunting for liquid helium and other scarce commodities while hoping to experience probably their most rewarding acquaintance, that is watching happy and satisfied users leaving their instruments loaded with tons of good data, the job of beamline scientist offers a lot more. From time to time we are called to share our expertise by serving on various study panels and committees. A few months ago, I was invited by the Deutsche Forschungsgemeinschaft to work with a group of experts helping to distribute millions of Euros between proposals submitted in a response to the new priority program. The job which included reviewing proposals and attending the meeting in Berlin was exhausting but very rewarding.
Apr. 2013
We had a smooth start after the shutdown. Beam got right back to the same spot where it used to be in January. We do not yet have numbers for the flux and the resolution but it looks like the photon flux has increased a bit and it seems that the energy resolution might have improved a bit as well.
The user program has resumed with the first user groups coming from UC Berkeley (A. Lanzara) and UC Boulder (D. Dessau). The former group has contributed a paper into the ALS data-base by publishing results of their recent study of graphene in Physical Review Letters (Phys. Rev. Lett 110, 146802).
July 2013
The Advanced Light Source has always been recognized for its successful programs on photoemission. Our photoemission facilities are employed by a diverse scientific community representing nearly every branch of condensed matter physics. This well-established technique is posed to capitalize on the capabilities offered by the new light source facilities. Recently I have helped to organize a one day workshop “Photoemission Spectroscopy - the upcoming decades” (http://pml.nist.gov/Meetings/SRI2013/program/workshop-5.html) which was held during the SRI-2013 conference at NIST (June19-21, NIST, Gaithersburg, MD). The workshop, which included 13 invited presentations by speakers from the United States, France, Germany and Italy, was well attended by the conferees. The talks encompassed recent studies of magnetic and strongly correlated materials with time resolved photoemission spectroscopy; instrumentation developments enabling such studies using HHG`s and FEL`s, and theoretical aspects of pump/probe photoemission experiments. The latter topic was highlighted by James Freericks from Georgetown University. Oliver Gessner (Lawrence Berkeley National Lab.), who has lead the first time resolved photoemission work conducted at the LCLS in Stanford, talked about studies of charge transfer in dye-sensitized nano-crystals.
Research opportunities provided by the new photoemission instruments, synchrotron beamlines and FEL facilities were outlined by Alexei Barinov (ELTTRA), Fausto Sirotti (SOLEIL), Serguei Molodtsov (European XFEL) and Stephen Benson (Jefferson Lab.). Christopher Smallwood (UC Berkeley), Stephan Mathias (University of Kaiserslautern), Marino Marci (University of Paris Sud) and Tomasz Durakiewic (Los Alamos National Lab.) talked about studies of strongly correlated materials using laboratory based HHG sources. They also gave an overview of the latest developments in the high harmonic generation laser sources. Much attention has been paid to the photoemission studies of electron spins in “classic” magnetic materials as well as topological insulators whose peculiar spin structure holds many promises. Martin Teichmann (Max-Born Institute Berlin and Free University Berlin) has talked about ultrafast demagnetization dynamics in gadolinium, while Dan Dessau (University of Colorado Boulder) and Nuh Gedick (Massachusetts Institute of Technology) presented photoemission studies of the helical spin structure in topological insulators.
It was clear that this community practicing all aspects of time resolved photoemission spectroscopy is producing very interesting data, which is often leading to dramatic advances in various areas of fundamental and applied research. The participants emphasized the need for the development of a FEL facility targeted specifically towards ultrafast time-resolved photoemission. Decades of photoemission research at the synchrotron beamlines have proved that ~10 to~150 eV is the most useful range of photon energies. Successful photoemission experiments at an FEL will likely rely on such energies as well.
Aug. 2013
Things were going along as usual. Work done at the beamline contributed to the paper published at Phys Rev. B Rapid Communications: http://prb.aps.org/abstract/PRB/v88/i4/e041101. A few other interesting papers have been accepted. They will be highlighted later.
Sept. 2013
Two groups have consumed the bulk of the beamtime in September: Dong Qian (Shanghai Jiao Tong University) studied thin films of bismuth and Shuyun Zhou (Tsinghua University) looked at various topological insulators. Collaboration with the latter group has produced a paper in Nature Physics
Collaboration with the Princeton University and Brookhaven Lab has resulted in the paper published in the Phys. Rev. B
Oct. 2013
Every cloud has a silver lining: An unexpected delay regarding the spin-ARPES instrument has freed up manpower to apply finishing touches to the photoemission spectrometer equipped with a high-photon-flux Gammadata helium lamp. Such an instrument has always been regarded as a highly desirable addition to the regular ARPES experiment stationed at the beamline since it permits many preparatory studies to be carried out in the "off-line" mode, hence saving precious beam-time and providing fresh users with a nice opportunity to get "hands-on" experience with the ARPES instrumentation. In the middle of October, this instrument saw its first real action and entertained a group from the University of Colorado, Boulder, which used the instrument for several days and tried out new samples and ideas without consuming any of their shifts allocated for the present cycle. The instrument performed well.

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