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Terasawa, Tomoo; Matsunaga, Kazuya*; Hayashi, Naoki*; Ito, Takahiro*; Tanaka, Shinichiro*; Yasuda, Satoshi; Asaoka, Hidehito
Vacuum and Surface Science, 66(9), p.525 - 530, 2023/09
As Au (001) surfaces exhibit a quasi-one-dimensional corrugated structure, Hex-Au(001), its periodicity was predicted to change the electronic structure of graphene when graphene was grown on this surface. Furthermore, the hybridization between graphene and Au is known to introduce bandgap and spin polarization into graphene. Here, we report angle-resolved photoemission spectroscopy and density functional theory calculation of graphene on a Hex-Au(001) surface. A bandgap of 0.2 eV in the graphene Dirac cone was observed at the crossing point of the graphene Dirac cone and Au 6sp bands, indicating that the origin of the bandgap formation was the hybridization between the graphene Dirac cone and Au 6sp band. We discussed the hybridization mechanism and anticipated spin injection into the graphene Dirac cone.
Terasawa, Tomoo; Matsunaga, Kazuya*; Hayashi, Naoki*; Ito, Takahiro*; Tanaka, Shinichiro*; Yasuda, Satoshi; Asaoka, Hidehito
Physical Review Materials (Internet), 7(1), p.014002_1 - 014002_10, 2023/01
Times Cited Count：4 Percentile：82.04(Materials Science, Multidisciplinary)Au(001) surfaces exhibit a complex reconstructed structure [Hex-Au(001)] comprising a hexagonal surface and square bulk lattices, yielding a quasi-one-dimensional corrugated surface. When graphene was grown on this surface, the periodicity of the corrugated surface was predicted to change the electronic structure of graphene, forming bandgaps and new Dirac points. Furthermore, the graphene-Au interface is promising for bandgap generation and spin injection due to band hybridization. Here, we report the angle-resolved photoemission spectroscopy and density functional calculation of graphene on a Hex-Au(001) surface. The crossing point of the original and replica graphene 
bands showed no bandgap, suggesting that the one-dimensional potential was too small to modify the electronic structure. A bandgap of 0.2 eV was observed at the crossing point of the graphene and Au 
bands, indicating that the bandgap is generated using hybridization of the graphene and Au bands. We discussed the hybridization mechanism and concluded that the R30 configuration between graphene and Au and an isolated electronic structure of Au are essential for effective hybridization between graphene and Au. We anticipate that hybridization between graphene and Au would result in spin injection into graphene.
layers in the triple-layer cuprate BiSrCaCu
O
studied by angle-resolved photoemission spectroscopyIdeta, Shinichiro*; Johnston, S.*; Yoshida, Teppei*; Tanaka, Kiyohisa*; Mori, Michiyasu; Anzai, Hiroaki*; Ino, Akihiro*; Arita, Masashi*; Namatame, Hirofumi*; Taniguchi, Masaki*; et al.
Physical Review Letters, 127(21), p.217004_1 - 217004_6, 2021/11
Times Cited Count：6 Percentile：59.12(Physics, Multidisciplinary)
Ge in the normal stateNakatani, Yasuhiro*; Aratani, Hidekazu*; Fujiwara, Hidenori*; Mori, Takeo*; Tsuruta, Atsushi*; Tachibana, Shoichi*; Yamaguchi, Takashi*; Kiss, Takayuki*; Yamasaki, Atsushi*; Yasui, Akira*; et al.
Physical Review B, 97(11), p.115160_1 - 115160_7, 2018/03
Times Cited Count：5 Percentile：25.26(Materials Science, Multidisciplinary)Yamasaki, Atsushi*; Fujiwara, Hidenori*; Tachibana, Shoichi*; Iwasaki, Daisuke*; Higashino, Yuji*; Yoshimi, Chiaki*; Nakagawa, Koya*; Nakatani, Yasuhiro*; Yamagami, Kohei*; Aratani, Hidekazu*; et al.
Physical Review B, 94(11), p.115103_1 - 115103_10, 2016/11
Times Cited Count：17 Percentile：60.7(Materials Science, Multidisciplinary)In this study, we systematically investigate three-dimensional(3D) momentum-resolved electronic structures of Ruddlesden-Popper-type iridium oxides Sr
Ir
O
using soft-X-ray angle-resolved photoemission spectroscopy (SX-ARPES). Our results provide direct evidence of an insulator-to-metal transition that occurs upon increasing the dimensionality of the IrO-plane structure. This transition occurs when the spin-orbit-coupled 
= 1/2 band changes its behavior in the dispersion relation and moves across the Fermi energy. By scanning the photon energy over 350 eV, we reveal the 3D Fermi surface in SrIrO
and 
-dependent oscillations of photoelectron intensity in SrIrO
. To corroborate the physics deduced using low-energy ARPES studies, we propose to utilize SX-ARPES as a powerful complementary technique, as this method surveys more than one whole Brillouin zone and provides a panoramic view of electronic structures.
electrons in Ce
In
(=Rh, Ir)Fujimori, Shinichi; Okane, Tetsuo; Okamoto, Jun; Mamiya, Kazutoshi; Muramatsu, Yasuji; Fujimori, Atsushi*; Harima, Hisatomo*; Aoki, Dai*; Ikeda, Shugo*; Shishido, Hiroaki*; et al.
Physical Review B, 67(14), p.144507_1 - 144507_5, 2003/04
Times Cited Count：35 Percentile：79.83(Materials Science, Multidisciplinary)We have performed angle-resolved photoemission spectroscopy (
~eV) and 3
-4 resonant photoemission spectroscopy (
~eV) studies on the layered cerium compounds CeIn (=Rh and Ir), which show competition between superconductivity and antiferromagnetism. The results suggest that the Ce~4 electrons in both compounds are nearly localized. We have found that although the Ce~4 electrons in the superconducting CeIrIn are more delocalized than those in the antiferromagnetic CeRhIn, their electronic structures are very similar to each other.
Br]BrFujimori, Shinichi; Ino, Akihiro; Okane, Tetsuo; Fujimori, Atsushi; Okada, Kozo*; Manabe, Toshio*; Yamashita, Masahiro*; Kishida, Hideo*; Okamoto, Hiroshi*
Surface Review and Letters, 9(2), p.1065 - 1069, 2002/04
Times Cited Count：0 Percentile：0(Chemistry, Physical)no abstracts in English
and CeIrInFujimori, Shinichi; Ino, Akihiro; Okane, Tetsuo; Fujimori, Atsushi; Harima, Hisatomo*; Aoki, Dai*; Ikeda, Shugo*; Shishido, Hiroaki*; Haga, Yoshinori; Tokiwa, Yoshifumi; et al.
Physica B; Condensed Matter, 312-313, p.132 - 133, 2002/03
Times Cited Count：1 Percentile：7.75(Physics, Condensed Matter)We have performed angle resolved photoemission experiments on heavy-fermion compounds CeRhIn and CeIrIn. The obtained spectra are compared with the results of the full-potential linear-augmented-plane-wave (FLAPW) band-structure calculations, treating the Ce 4 electrons as being itinerant. The spectral contributions from the ligand Rh, Ir or In states were well reproduced by the calculations, although the features originated from Ce 4 states near 
were not clearly observed.
fullerene absorbent for Cs-135 isotope separation, studied by photoelectron spectroscopySekiguchi, Tetsuhiro; Yokoyama, Keiichi; Uozumi, Yuki*; Yano, Masahiro; Asaoka, Hidehito; Suzuki, Shinichi; Yaita, Tsuyoshi
no journal, ,
For nuclear transmutation of cesium-135 (Cs-135), which is long-lived fission product, we are developing selective absorbent which takes only Cs atom in, but does not CsI. In this study, absorbing property of Cs atom or CsI into fullerene (C) solid has been investigated using synchrotron-based angle-dependent X-ray photoelectron spectroscopy (ARXPS). It was found that Cs penetrates into C deep bulk. In contrast, CsI does not diffuse into bulk, although CsI over-layer was formed on the shallow surface. Furthermore, XPS spectra were measured as a function of Ar
-sputtering time in order to know Cs concentration profiles in further deep region. Results showed that Cs penetrates into deep region of several hundreds 
.
Terasawa, Tomoo; Yasuda, Satoshi; Matsunaga, Kazuya*; Hayashi, Naoki*; Tanaka, Shinichiro*; Norimatsu, Wataru*; Ito, Takahiro*; Machida, Shinichi*; Asaoka, Hidehito
no journal, ,
Graphene grown on Hex-Au(001) substrate shows an energy gap in its -band. Previous reports speculated that the periodic potential of Hex-Au(001) resulted in the energy gap formation in the -band of graphene. In the present study, we found by angle-resolved photoemission spectroscopy that the hybridyzation of sp-band of Hex-Au(001) and -band of graphene created the energy gap in the -band of graphene.
Terasawa, Tomoo; Matsunaga, Kazuya*; Hayashi, Naoki*; Ito, Takahiro*; Tanaka, Shinichiro*; Yasuda, Satoshi; Asaoka, Hidehito
no journal, ,
As a Hex-Au(001) surface shows one-dimensional corrugation and is chemically inert, it has been employed to study the effect of one-dimensional potential on graphene. Such potential has been expected to make the band structure of graphene anisotropic, which shows the mini-gap at the zone boundary across the potential and the high group velocity along the potential. However, the bandgap in the graphene on Hex-Au(001) was only indirectly suggested by scanning tunneling spectroscopy. Here, we report the band structure of graphene on Hex-Au(001) substrates using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculation. The ARPES image shows the bandgap in the graphene band close to the Au 6sp band. The DFT calculated band structure shows the bandgap not at the crossing point of the graphene bands but that of graphene and Au 6sp bands. We thus conclude that the bandgap originates from the hybridization between graphene and Au. This hybridization is similar to that observed in the graphene and Au interface on the SiC substrate. We expect that the hybridization between graphene and Au is essential as the Rashba splitting of 100 meV was observed around the gap.
Terasawa, Tomoo
no journal, ,
Graphene, a two-dimensional material consisting of a honeycomb lattice of C atoms, has attracted much attention from basic physics to applications because of its extremely high carrier mobility and half-integer quantum Hall effect. Since a choice of substrate affects the properties of graphene, the synthesis and properties of graphene on various substrates have been the subject of surface science research. The interface between graphene and Au is expected in the field of spintronics because Au has a large atomic number and a large spin-orbit interaction. On the other hand, the atomic configuration in this interface is often unknown, and therefore, the angle-resolved photoemission spectroscopy (ARPES) experiments and density functional theory (DFT) calculations do not match each other for this interface. Here, we report the band structure of graphene on the Hex-Au(001) reconstructed surface using ARPES and DFT calculations. Since the solubility of C in Au is very low, graphene can be grown on Au surfaces by chemical vapor deposition (CVD). Hex-Au(001) reconstruction was kept even after the CVD growth of graphene. Therefore, the ARPES measurement was carried out for graphene on the well-known atomic configuration of Hex-Au(001). The ARPES intensity map shows the bandgap in the graphene pi band close to the Au 6sp band. The DFT calculated band structure shows the bandgap at the crossing point of the graphene pi and Au 6sp bands. We discuss that the bandgap originates from the hybridization between graphene and Au, similar to the case of graphene and Au interface on the SiC substrate. As the Rashba splitting of 100 meV was observed in the graphene and Au interface on the SiC substrate, we expect that the hybridization between graphene and Au is essential for the future applications of graphene for spintronic devices.
