Angle-Resolved Photoemission Spectroscopy

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Takafumi Sato - One of the best experts on this subject based on the ideXlab platform.

  • Superstructure-dependent electronic states in CaAlSi superconductors studied by Angle-Resolved Photoemission Spectroscopy
    Physical Review B, 2015
    Co-Authors: Takafumi Sato, Katsuaki Sugawara, Seigo Souma, Jun Akimitsu, Y. X. Xiao, Kosuke Nakayama, S. Kuroiwa, Takashi Takahashi
    Abstract:

    We have performed high-resolution Angle-Resolved Photoemission Spectroscopy on layered polymorph series of $1H\ensuremath{-}, 5H\ensuremath{-}$, and $6H\ensuremath{-}\mathrm{CaAlSi}$, which exhibit superconductivity below 6.5, 5.7, and 7.7 K, respectively. While the overall band structure in the valence-band region is similar among these compounds, the volume of the Fermi surface at the $M$ point and the magnitude of the superconducting gap are markedly different from each other. Implications of such variation in the electronic structure due to the superstructure along the $c$ axis are discussed in relation to the physical properties of CaAlSi.

  • Fe-based superconductors: an Angle-Resolved Photoemission Spectroscopy perspective
    Reports on Progress in Physics, 2011
    Co-Authors: Pierre Richard, Takafumi Sato, Takashi Takahashi, K. Nakayama, Hong Ding
    Abstract:

    Angle-Resolved Photoemission Spectroscopy allows direct visualization and experimental determination of the electronic structure of crystals in the momentum space, including the precise characterization of the Fermi surface and the superconducting order parameter. It is thus particularly suited for investigating multi-band systems such as the Fe-based superconductors. In this review, we cover several aspects of these recently discovered materials that have been addressed by this technique, with a special emphasis on their superconducting gap and their Fermi surface topology. We provide sufficient experimental evidence to support the reliability and the consistency of the Angle-Resolved Photoemission Spectroscopy measurements over a wide range of material compositions.

  • Angle-Resolved Photoemission Spectroscopy of Graphene, Graphite, and Related Compounds
    Comprehensive Semiconductor Science and Technology, 2011
    Co-Authors: Takafumi Sato, Takashi Takahashi
    Abstract:

    High-resolution Angle-Resolved Photoemission Spectroscopy (ARPES) studies on carbon-based materials, such as graphene, graphite, and graphite intercalation compounds (GICs), are presented. We briefly review the basic principle of ARPES technique as well as the recent development of experimental apparatus, and then focus on the electronic structure in the vicinity of the Fermi level responsible for novel physical properties. We discuss the energy band structure and the Fermi surface of graphene and graphite in terms of the many-body interaction, the edge-localized states, and the Dirac-fermion-like behavior. We also explain the first direct ARPES observation of the interlayer band and the superconducting gap in a high-Tc GIC, C6Ca.

  • Three-dimensional band structure of highly metallic Na0.8WO3 by Angle-Resolved Photoemission Spectroscopy
    Physical Review B, 2009
    Co-Authors: Satyabrata Raj, Takafumi Sato, Takashi Takahashi, Anirban Chakraborty, Debraj Choudhury, Priya Mahadevan, Jun Fujii, Ivana Vobornik, D. D. Sarma
    Abstract:

    Three-dimensional electronic structure of highly metallic sodium tungsten bronze, Na0.8WO3, is investigated by high-resolution Angle-Resolved Photoemission Spectroscopy. The experimentally determined valence-band structure along the momentum directions both parallel and perpendicular to the surface has been compared with the results of ab initio band-structure calculation. The Angle-Resolved Photoemission Spectroscopy spectra for different photon energies reveal that possibly the oxygen vacancies in the system are responsible for the evolution of density of states at the top of Gamma point in experimental valence band. The band dispersion around Gamma(X) point leading to an electronlike Fermi surface is well predicted by the band calculation. As we move from bulk-sensitive to more-surface-sensitive photon energy, we found emergence of Fermi surfaces at X(M) and M(R) points similar to the one at Gamma(X) point, suggesting the reconstruction of surface due to rotation/deformation of WO6 octahedra.

  • Fermi Surface and Band Dispersions of MxCoO2 (M: Na, K, and Rb) Studied by Angle-Resolved Photoemission Spectroscopy
    Journal of the Physical Society of Japan, 2007
    Co-Authors: Toshiyuki Arakane, Takafumi Sato, Takashi Takahashi, Hong Ding, Takenori Fujii, Atsushi Asamitsu
    Abstract:

    We have performed Angle-Resolved Photoemission Spectroscopy (ARPES) on MxCoO2 (M: Na, K, and Rb) with both soft X-ray and ultraviolet light to clarify the electronic structure intrinsic to the bulk CoO2 plane. We observed a large holelike a(1g) Fermi surf

Takashi Takahashi - One of the best experts on this subject based on the ideXlab platform.

  • Superstructure-dependent electronic states in CaAlSi superconductors studied by Angle-Resolved Photoemission Spectroscopy
    Physical Review B, 2015
    Co-Authors: Takafumi Sato, Katsuaki Sugawara, Seigo Souma, Jun Akimitsu, Y. X. Xiao, Kosuke Nakayama, S. Kuroiwa, Takashi Takahashi
    Abstract:

    We have performed high-resolution Angle-Resolved Photoemission Spectroscopy on layered polymorph series of $1H\ensuremath{-}, 5H\ensuremath{-}$, and $6H\ensuremath{-}\mathrm{CaAlSi}$, which exhibit superconductivity below 6.5, 5.7, and 7.7 K, respectively. While the overall band structure in the valence-band region is similar among these compounds, the volume of the Fermi surface at the $M$ point and the magnitude of the superconducting gap are markedly different from each other. Implications of such variation in the electronic structure due to the superstructure along the $c$ axis are discussed in relation to the physical properties of CaAlSi.

  • Fe-based superconductors: an Angle-Resolved Photoemission Spectroscopy perspective
    Reports on Progress in Physics, 2011
    Co-Authors: Pierre Richard, Takafumi Sato, Takashi Takahashi, K. Nakayama, Hong Ding
    Abstract:

    Angle-Resolved Photoemission Spectroscopy allows direct visualization and experimental determination of the electronic structure of crystals in the momentum space, including the precise characterization of the Fermi surface and the superconducting order parameter. It is thus particularly suited for investigating multi-band systems such as the Fe-based superconductors. In this review, we cover several aspects of these recently discovered materials that have been addressed by this technique, with a special emphasis on their superconducting gap and their Fermi surface topology. We provide sufficient experimental evidence to support the reliability and the consistency of the Angle-Resolved Photoemission Spectroscopy measurements over a wide range of material compositions.

  • Angle-Resolved Photoemission Spectroscopy of Graphene, Graphite, and Related Compounds
    Comprehensive Semiconductor Science and Technology, 2011
    Co-Authors: Takafumi Sato, Takashi Takahashi
    Abstract:

    High-resolution Angle-Resolved Photoemission Spectroscopy (ARPES) studies on carbon-based materials, such as graphene, graphite, and graphite intercalation compounds (GICs), are presented. We briefly review the basic principle of ARPES technique as well as the recent development of experimental apparatus, and then focus on the electronic structure in the vicinity of the Fermi level responsible for novel physical properties. We discuss the energy band structure and the Fermi surface of graphene and graphite in terms of the many-body interaction, the edge-localized states, and the Dirac-fermion-like behavior. We also explain the first direct ARPES observation of the interlayer band and the superconducting gap in a high-Tc GIC, C6Ca.

  • Three-dimensional band structure of highly metallic Na0.8WO3 by Angle-Resolved Photoemission Spectroscopy
    Physical Review B, 2009
    Co-Authors: Satyabrata Raj, Takafumi Sato, Takashi Takahashi, Anirban Chakraborty, Debraj Choudhury, Priya Mahadevan, Jun Fujii, Ivana Vobornik, D. D. Sarma
    Abstract:

    Three-dimensional electronic structure of highly metallic sodium tungsten bronze, Na0.8WO3, is investigated by high-resolution Angle-Resolved Photoemission Spectroscopy. The experimentally determined valence-band structure along the momentum directions both parallel and perpendicular to the surface has been compared with the results of ab initio band-structure calculation. The Angle-Resolved Photoemission Spectroscopy spectra for different photon energies reveal that possibly the oxygen vacancies in the system are responsible for the evolution of density of states at the top of Gamma point in experimental valence band. The band dispersion around Gamma(X) point leading to an electronlike Fermi surface is well predicted by the band calculation. As we move from bulk-sensitive to more-surface-sensitive photon energy, we found emergence of Fermi surfaces at X(M) and M(R) points similar to the one at Gamma(X) point, suggesting the reconstruction of surface due to rotation/deformation of WO6 octahedra.

  • Fermi Surface and Band Dispersions of MxCoO2 (M: Na, K, and Rb) Studied by Angle-Resolved Photoemission Spectroscopy
    Journal of the Physical Society of Japan, 2007
    Co-Authors: Toshiyuki Arakane, Takafumi Sato, Takashi Takahashi, Hong Ding, Takenori Fujii, Atsushi Asamitsu
    Abstract:

    We have performed Angle-Resolved Photoemission Spectroscopy (ARPES) on MxCoO2 (M: Na, K, and Rb) with both soft X-ray and ultraviolet light to clarify the electronic structure intrinsic to the bulk CoO2 plane. We observed a large holelike a(1g) Fermi surf

Seigo Souma - One of the best experts on this subject based on the ideXlab platform.

Yoshichika Ōnuki - One of the best experts on this subject based on the ideXlab platform.

Takahiro Ito - One of the best experts on this subject based on the ideXlab platform.

  • Orbital-dependent electron correlation in LiFeAs revealed by Angle-Resolved Photoemission Spectroscopy
    Physical Review B, 2016
    Co-Authors: Tetsuya Hajiri, Takahiro Ito, Yong Seung Kwon, Masaharu Matsunami, B. H. Min, Kazuhiko Kuroki, S. Kimura
    Abstract:

    We report on the electronic structure of the 111-type iron pnictide superconductor LiFeAs as a function of temperature using Angle-Resolved Photoemission Spectroscopy. Below approximately 50 K, both the ${d}_{yz}$ hole band at the $Z$ point and the ${d}_{xz/yz}$ electron band at the $A$ point shift to a higher binding energy side. However, at the high-symmetry points $Z,\phantom{\rule{0.16em}{0ex}}A,\phantom{\rule{0.16em}{0ex}}\mathrm{\ensuremath{\Gamma}}$, and $M$, the remaining bands are almost independent of temperature. One of the possible scenarios for these observations is that a strong, three-dimensional orbital-dependent correlation exists in the normal state of LiFeAs in relation to short-range spin fluctuations.

  • Band structure ofUPd3studied by ultrahigh-resolution Angle-Resolved Photoemission Spectroscopy
    Physical Review B, 2002
    Co-Authors: Takahiro Ito, Seigo Souma, Hiroshi Kumigashira, Yoshinori Haga, Yoshihumi Tokiwa, T. Takahashi, Yoshichika Ōnuki
    Abstract:

    We have performed ultrahigh-resolution Angle-Resolved Photoemission Spectroscopy on UPd 3 to study the band structure near the Fermi level (E F ) and the Fermi surface. We found three Fermi surfaces (FS's): two hole pockets with a dominant Pd 4d character at the Γ (A) point and an electron pocket with a U 6d nature at the K (H) point. These FS's are qualitatively well reproduced in the band structure calculation based on the localized U-5f-electron model, while remarkable quantitative discrepancies are observed near E F . The U 5f states are located 0.4-1.0 eV below E F and do not contribute to the Fermi surface. These results indicate the strongly localized nature of U 5f electrons in UPd 3 .

  • Electronic structure of black SmS. II. Angle-Resolved Photoemission Spectroscopy
    Physical Review B, 2002
    Co-Authors: Takahiro Ito, Takashi Takahashi, Hiroshi Kumigashira, Ashish Chainani, Noriaki K. Sato
    Abstract:

    We have studied the electronic band structure of semiconducting black SmS with high-resolution Angle-Resolved Photoemission Spectroscopy (ARPES). The valence band consists of two well-separated groups of bands: almost nondispersive bands near E F and highly dispersive bands at higher binding energy. The former is ascribed to the Sm 2 (4f 6 →4f 5 ) multiplet and the latter to mainly the S 3p states. We found a small but distinct energy dispersion in the Sm 4f-derived bands near E F . This indicates a strong hybridization between the "localized" Sm 4f electrons and the "itinerant" conduction electrons, leading to the "delocalized" Sm 4f states in mixed-valent SmS. We have compared the present ARPES results with a recent periodic Anderson model calculation [C. Lehner et al., Phys. Rev. B 58, 6807 (1998)].

  • Ultrahigh-resolution Angle-Resolved Photoemission Spectroscopy of UPd3
    Physica B-condensed Matter, 2001
    Co-Authors: Takahiro Ito, Seigo Souma, Takashi Takahashi, Hiroshi Kumigashira, Yoshinori Haga, Yoshihumi Tokiwa, Yoshichika Ōnuki
    Abstract:

    Abstract We have studied the electronic band structure and the Fermi surface of UPd 3 with ultrahigh-resolution Angle-Resolved Photoemission Spectroscopy. It was found that non-dispersive U 5f “bands” are located far below the Fermi level and the main body of valence band consists of Pd 4d-U 6d hybridized dispersive bands in qualitatively good agreement with the band-structure calculation based on the localized U 5f model. We found two hole-like Fermi surfaces with a dominant Pd 4d character at Γ ( A ) point and an electron-like one with a U 6d nature at K( H ) point.

  • Angle-Resolved Photoemission Spectroscopy of UPt3
    Physica B-condensed Matter, 1999
    Co-Authors: Takahiro Ito, Takashi Takahashi, Hiroshi Kumigashira, Hyeong-do Kim, Noriaki Kimura, Yoshinori Haga, E. Yamamoto, Yoshichika Ōnuki, Hisatomo Harima
    Abstract:

    Abstract We have performed Angle-Resolved Photoemission Spectroscopy on UPt3. The experimental result has been compared with the band structure calculation including the U 5f states. The overall feature of Pt 5d bands shows a good agreement between experiment and calculation, while the experimental U 5f band is much narrower, indicative of the strong renormalization.