2015S2-005
酸化物量子井戸構造に誘起される新奇2次元電子状態とその機能探索

Last modified 2022-05-16 by s-proposalpfiqst.kek.jp

●基本情報
　●実験責任者：組頭　広志（KEK-PF）
　●課題有効期間：2015/10〜2018/9
　●実験ステーション：2A/B, 16A, 4C, 7C

●課題の概要
　強相関酸化物と呼ばれる遷移金属酸化物は、電荷・スピン・軌道の自由度が複雑に絡み合うことで高温超伝導に代表される類い希な物性を示す。近年、物質設計の自由度が高い「超構造」を用いて、これらの強相関酸化物の示す異常な物性を制御しようという研究が物性物理学の一つの大きな潮流となっている。その中でも、酸化物量子井戸構造を用いた強相関電子の量子閉じ込めは、次元性の低下に伴った強相関電子の振る舞いを調べるうえで非常に有効な手法として注目されている。強相関酸化物超構造の作製が可能になったことで、1.量子井戸構造による強相関電子の2次元閉じ込め、２．バンド絶縁体同士の界面における高移動度2次元電子ガスの形成、３．量子常誘電体における表面2次元電子ガスの形成とラシュバ効果、等の注目すべき「超構造における2次元電子状態」が報告されている。
　本研究の目的は、酸化物量子井戸構造を用いて新奇な2次元電子状態を創成することにある。そのために、放射光解析に基づく量子物質開発「Materials by design」というスキームを提案・実行する。具体的には、電子論的パラメータを制御した強相関量子井戸構造を設計・製作し、その量子化状態をその場放射光電子分光により直接決定する。この放射光解析に基づく原子レベルでの構造、電子・磁気・軌道状態、等の理解を通して、低次元強相関量子状態の設計・制御のための指針を導き出すことを大きな目標としている。さらには、「設計指針の確立」にとどまらず、本S2課題メンバー内の薄膜作製グループとの密接な連携を通して実際の超構造・デバイスの製作、およびその量子物性評価を行う。
　本S2課題では、主に放射光電子分光による酸化物超構造の表面・界面研究を遂行することになる。これを、VUVとSXモードを切り替えることで、広エネルギー範囲にわたって高分解能かつ高強度の放射光を供給できる新BL2Aを駆使して行う。この「酸化物表面・界面解析ビームライン」に「in-situ光電子分光+酸化物MBE複合装置」を設置し、実験ステーションの高度化・最適化を行う。これにより、酸化物のみならず機能性材料科学における「放射光解析プラットホーム」を構築・運営することで、放射光解析に基づく物質開発を推進する。

●成果発表
　●論文

• "Intervalence charge transfer and charge transport in the spinel ferrite ferromagnetic semiconductor Ru-doped CoFe₂O₄"
  Masaki Kobayashi, Munetoshi Seki, Masahiro Suzuki, Ryo Okano, Miho Kitamura, Koji Horiba, Hiroshi Kumigashira, Atsushi Fujimori, Masaaki Tanaka, and Hitoshi Tabata
  Phys. Rev. B, 105 (2022) 205103.
• "High-Quality Few-Layer Graphene on Single-Crystalline SiC thin Film Grown on Affordable Wafer for Device Applications"
  Norifumi Endoh, Shoji Akiyama, Keiichiro Tashima, Kento Suwa, Takamasa Kamogawa, Roki Kohama, Kazutoshi Funakubo, Shigeru Konishi, Hiroshi Mogi, Minoru Kawahara, Makoto Kawai, Yoshihiro Kubota, Takuo Ohkochi, Masato Kotsugi, Koji Horiba, Hiroshi Kumigashira, Maki Suemitsu, Issei Watanabe and Hirokazu Fukidome
  Nanmaterials, 11 (2021) 392.
• "Influence of fluorination on electronic states and electron transport properties of Sr₂IrO₄ thin films"
  Takahiro Maruyama, Akira Chikamatsu, Tsukasa Katayama, Kenta Kuramochi, Hiraku Ogino, Miho Kitamura, Koji Horiba, Hiroshi Kumigashira and Tetsuya Hasegawa
  J. Mater. Chem. C, 8 (2020) 8268.
• "Bottom-current-collector-free thin-film batteries using LiNi_0.8Co_0.2O₂ epitaxial thin films"
  Kazunori Nishio, Koji Horiba, Naoto Nakamura, Miho Kitamura, Hiroshi Kumigashira, Ryota Shimizu, Taro Hitosugi
  J. Power Sources, 416 (2019) 56.
• "Relationship between charge redistribution and ferromagnetism at the heterointerface between the perovskite oxides LaNiO₃ and LaMnO₃"
  Miho Kitamura, Masaki Kobayashi, Enju Sakai, Makoto Minohara, Ryu Yukawa, Daisuke Shiga, Kenta Amemiya, Yosuke Nonaka, Goro Shibata, Atsushi Fujimori, Hiroshi Fujioka, Koji Horiba, and Hiroshi Kumigashira
  Phys. Rev. B, 100 (2019) 245132.
• "Improved crystalline quality and electric conductivity in infinite-layer SrFeO₂ films through Sm substitution"
  Tsukasa Katayama, Akira Chikamatsu, Hiroshi Kumigashira, and Tetsuya Hasegawa
  Appl. Phys. Lett., 114 (2019) 232906.
• "In-gap state generated by La-on-Sr substitutional defects within the bulk of SrTiO₃"
  Yoshihiro Aiura, Kenichi Ozawa, Yasuhisa Tezuka, Makoto Minohara, Akane Samizo, Kyoko Bando, Hiroshi Kumigashira and Kazuhiko Mase
  Phys. Chem. Chem. Phys., 21 (2019) 14646.
• "Emergence of metallic monoclinic states of VO₂ films induced by K deposition"
  D. Shiga, M. Minohara, M. Kitamura, R. Yukawa, K. Horiba, and H. Kumigashira
  Phys. Rev. B, 99 (2019) 125120.
• "Crystal structure of high-performance thermoelectric materials by high resolution neutron powder diffraction"
  Peng Wu, Yoshihisa Ishikawa, Masato Hagihala, Sanghyun Lee, Kunling Peng, Guoyu Wang, Shuki Torii, Takashi Kamiyama
  Physica B: Condensed Matter, 551 (2018) 64.
• "Electronic properties across metal-insulator transition in β-pyrochlore-type CsW₂O₆ epitaxial films"
  Takuto Soma, Kohei Yoshimatsu, Koji Horiba, Hiroshi Kumigashira, and Akira Ohtomo
  Phys. Rev. Materials, 2 (2018) 115003.
• "Anomalous Electron Conduction of Nd_0.6Sr_0.4FeO_3-δ Thin Film with Lattice Distortion and Oxygen Vacancies"
  Wataru Namiki, Takashi Tsuchiya, Makoto Takayanagi, Kinya Kawamura, Takuya Kawaguchi, Tohru Higuchi
  Trans. Mat. Res. Soc. Jpn., 43 (2018) 175.
• "Surface Electronic Structure of Post-Annealed La_0.67Sr_0.33MnO₃ Epitaxial Thin Films on SrTiO₃(100)"
  Kinya Kawamura, Takashi Tsuchiya, Makoto Takayanagi, Wataru Namiki, Kazuya Terabe, Tohru Higuchi
  Trans. Mat. Res. Soc. Jpn., 43 (2018) 179.
• "Anisotropic Charge Distribution Induced by Spin Polarization in La_0.6Sr_0.4MnO₃ Thin Films Studied by X-ray Magnetic Linear Dichroism"
  Goro Shibata, Kohei Yoshimatsu, Keisuke Ishigami, Takayuki Harano, Yukio Takahashi, Shoya Sakamoto, Yosuke Nonaka, Toshiharu Kadono, Mitsuho Furuse, Schuichiro Fuchino, Makoto Okano, Jun-ichi Fujihira, Akira Uchida, Kazunori Watanabe, Hideyuki Fujihira, Seiichi Fujihira, Arata Tanaka, Hiroshi Kumigashira, Tsuneharu Koide, and Atsushi Fujimori
  J. Phys. Soc. Jpn., 87 (2018) 114713.
• "Unexpected metal-insulator transition in thick Ca_1-xSr_xVO₃ film on SrTiO₃ (100) single crystal"
  Makoto Takayanagi, Takashi Tsuchiya, Wataru Namiki, Shigenori Ueda, Makoto Minohara, Koji Horiba, Hiroshi Kumigashira, Kazuya Terabe, and Tohru Higuchi
  Appl. Phys. Lett., 112 (2018) 133106.
• "Large anisotropy in conductivity of Ti₂O₃ films"
  K. Yoshimatsu, H. Kurokawa, K. Horiba, H. Kumigashira, and A. Ohtomo
  AIP Materials, 6 (2018) 101101.
• "Growth of antiperovskite oxide Ca₃SnO films by pulsed laser deposition"
  Makoto Minohara, Ryu Yukawa, Miho Kitamura, Reiji Kumai, Youichi Murakami, Hiroshi Kumigashira
  J. Cryst. Growth, 500 (2018) 33.
• "Spatial coherence of the insulating phase in quasi-two-dimensional LaNiO₃ films"
  Masato Anada, Kazuhiro Kowa, Hiroki Maeda, Enju Sakai, Miho Kitamura, Hiroshi Kumigashira, Osami Sakata, Yoshinori Nakanishi-Ohno, Masato Okada, Tsuyoshi Kimura, and Yusuke Wakabayashi
  Phys. Rev. B, 98 (2018) 014105.
• "Control of two-dimensional electronic states at anatase TiO₂(001) surface by K adsorption"
  R. Yukawa, M. Minohara, D. Shiga, M. Kitamura, T. Mitsuhashi, M. Kobayashi, K. Horiba, and H. Kumigashira
  Phys. Rev. B, 97 (2018) 165428.
• "Converting topological insulators into topological metals within the tetradymite family"
  K.-W. Chen, N. Aryal, J. Dai, D. Graf, S. Zhang, S. Das, P. Le Fèvre, F. Bertran, R. Yukawa, K. Horiba, H. Kumigashira, E. Frantzeskakis, F. Fortuna, L. Balicas, A. F. Santander-Syro, E. Manousakis, and R. E. Baumbach
  Phys. Rev. B, 97 (2018) 165112.
• "Ferromagnetism with strong magnetocrystalline anisotropy in A-site ordered perovskite YBaCo₂O₆ epitaxial thin films prepared via wet-chemical topotactic oxidation"
  Tsukasa Katayama, Akira Chikamatsu, Yasushi Hirose, Makoto Minohara, Hiroshi Kumigashira, Isao Harayama, Daiichiro Sekiba and Tetsuya Hasegawaa
  J. Mater. Chem. 6 (2018) 3445.
• "Unexpected metal-insulator transition in thick Ca_1-xSr_xVO₃ film on SrTiO₃ (100) single crystal"
  Makoto Takayanagi, Takashi Tsuchiya, Wataru Namiki, Shigenori Ueda, Makoto Minohara, Koji Horiba, Hiroshi Kumigashira, Kazuya Terabe, and Tohru Higuchi
  Appl. Phys. Lett. 112 (2018) 133106.
• "High-density two-dimensional electron system induced by oxygen vacancies in ZnO"
  T. C. Rödel, J. Dai, F. Fortuna, E. Frantzeskakis, P. Le Fèvre, F. Bertran, M. Kobayashi, R. Yukawa, T. Mitsuhashi, M. Kitamura, K. Horiba, H. Kumigashira, and A. F. Santander-Syro
  Phys. Rev. Materials, 2 (2018) 051601(R).
• "Terahertz light-emitting graphene-channel transistor toward single-mode lasing"
  Deepika Yadav, Gen Tamamushi, Takayuki Watanabe, Junki Mitsushio, Youssef Tobah, Kenta Sugawara, Alexander A. Dubinov, Akira Satou, Maxim Ryzhii, Victor Ryzhii, Taiichi Otsuji
  Nanophotonics 7 (2018) 741.
• "Anisotropic spin-density distribution and magnetic anisotropy of strained La_1−xSr_xMnO₃ thin films: angle-dependent x-ray magnetic circular dichroism"
  Goro Shibata, Miho Kitamura, Makoto Minohara, Kohei Yoshimatsu, Toshiharu Kadono, Keisuke Ishigami, Takayuki Harano, Yukio Takahashi, Shoya Sakamoto, Yosuke Nonaka, Keisuke Ikeda, Zhendong Chi, Mitsuho Furuse, Shuichiro Fuchino, Makoto Okano, Jun-ichi Fujihira, Akira Uchida, Kazunori Watanabe, Hideyuki Fujihira, Seiichi Fujihira, Arata Tanaka, Hiroshi Kumigashira, Tsuneharu Koide & Atsushi Fujimori
  npj Quantum Materials, 3 (2018) 3.
• "Quasiparticle Interference on Cubic Perovskite Oxide Surfaces"
  Yoshinori Okada, Shiue-Yuan Shiau, Tay-Rong Chang, Guoqing Chang, Masaki Kobayashi, Ryota Shimizu, Horng-Tay Jeng, Susumu Shiraki, Hiroshi Kumigashira, Arun Bansil, Hsin Lin, and Taro Hitosugi
  Phys. Rev. Lett., 119 (2017) 086801.
• "Amorphous Gallium Oxide as an Improved Host for Inorganic Light-Emitting Thin Film Semiconductor Fabricated at Room Temperature on Glass"
  Naoto Watanabe, Junghwan Kim, Keisuke Ide, Hidenori Hiramatsu, Hiroshi Kumigashira, Shigenori Ueda, Hideo Hosono and Toshio Kamiya
  ECS J. Solid State Sci. Technol., 6 (2017) P410.
• "Emergence of Quantum Critical Behavior in Metallic Quantum-Well States of Strongly Correlated Oxides"
  Masaki Kobayashi, Kohei Yoshimatsu, Taichi Mitsuhashi, Miho Kitamura, Enju Sakai, Ryu Yukawa, Makoto Minohara, Atsushi Fujimori, Koji Horiba and Hiroshi Kumigashira
  Scientific Reports, 7 (2017) 16621.
• "Electronic Structures and Photoanodic Properties of Ilmenite-type MTiO₃ Epitaxial Films (M = Mn, Fe, Co, Ni)"
  K. Yoshimatsu, H. Mashiko, N. Umezawa, K. Horiba, H. Kumigashira, and A. Ohtomo
  J. Phys. Chem. C, 121 (2017) 18717.
• "Semimetallic bands derived from interlayer electrons in the quasi-two-dimensional electride Y₂C"
  Koji Horiba, Ryu Yukawa, Taichi Mitsuhashi, Miho Kitamura, Takeshi Inoshita, Noriaki Hamada, Shigeki Otani, Naoki Ohashi, Sachiko Maki, Jun-ichi Yamaura, Hideo Hosono, Youichi Murakami, and Hiroshi Kumigashira
  Phys. Rev. B, 96 (2017) 045101.
• "Electron Conduction of Nd_0.6Sr_0.4FeO_3−δ Thin Film with Oxygen Vacancies Prepared by RF Magnetron Sputtering"
  Wataru Namiki, Takashi Tsuchiya, Makoto Takayanagi, Shoto Furuichi, Makoto Minohara, Masaki Kobayashi, Koji Horiba, Hiroshi Kumigashira, and Tohru Higuchi
  J. Phys. Soc. Jpn., 86 (2017) 074704.
• "Surface Electronic Structure of Proton-doped YSZ Thin Film by Soft-X-ray Photoemission Spectroscopy"
  Makoto Takayanagi, Takashi Tsuchiya, Makoto Minohara, Masaki Kobayashi, Koji Horiba, Hiroshi Kumigashira, Tohru Higuchi
  Trans. Mat. Res. Soc. Jpn., 42 (2017) 61.
• "Structural and Electrical Properties of BaPrO_3-δ Thin Film with Oxygen Vacancies"
  Shoto Furuichi, Takashi Tsuchiya, Koji Horiba, Masaki Kobayashi, Makoto Minohara, Hiroshi Kumigashira, Tohru Higuchi
  Trans. Mat. Res. Soc. Jpn., 42 (2017) 15.
• "Resonant photoemission and X-ray absorption spectroscopies of lithiated magnetite thin film"
  Takashi Tsuchiya, Kinya Kawamura, Wataru Namiki, Shoto Furuichi, Makoto Takayanagi, Makoto Minohara, Masaki Kobayashi, Koji Horiba, Hiroshi Kumigashira, Kazuya Terabe and Tohru Higuchi
  Jpn. J. Appl. Phys., 56 (2017) 04CK01.
• "Proton Conduction on YSZ Electrolyte Thin Films Prepared by RF Magnetron Sputtering"
  Makoto Takayanagi, Shoto Furuichi, Wataru Namiki, Takashi Tsuchiya, Makoto Minohara, Masaki Kobayashi, Koji Horiba, Hiroshi Kumigashira, and Tohru Higuchi
  ECS Trans., 75 (2017) 115.
• "Ion Conduction of BaPrO_3-δ Thin Film with Mixed Valence State for SOFC Anode Electrode"
  Shoto Furuichi, Takashi Tsuchiya, Makoto Minohara, Masaki Kobayashi, Koji Horiba, Hiroshi Kumigashira, and Tohru Higuchi
  ECS Trans., 75 (2017) 99.
• "Electron-Ion Mixed Conduction of Nd_0.6Sr_0.4FeO₃ Cathode Electrode Thin Film for Solid Oxide Fuel Cell"
  Wataru Namiki, Makoto Takayanagi, Shoto Furuichi, Takashi Tsuchiya, Makoto Minohara, Masaki Kobayashi, Koji Horiba, Hiroshi Kumigashira, and Tohru Higuchi
  ECS Trans., 75 (2017) 83.
• "Reversible Changes in Resistance of Perovskite Nickelate NdNiO₃ Thin Films Induced by Fluorine Substitution"
  Tomoya Onozuka, Akira Chikamatsu, Tsukasa Katayama, Yasushi Hirose, Isao Harayama, Daiichiro Sekiba, Eiji Ikenaga, Makoto Minohara, Hiroshi Kumigashira, and Tetsuya Hasegawa
  ACS Appl. Mater. Interfaces, 9 (2017) 10882.
• "Interlayer states arising from anionic electrons in the honeycomb-lattice-based compounds AeAlSi (Ae=Ca, Sr, Ba)"
  Yangfan Lu, Tomofumi Tada, Yoshitake Toda, Shigenori Ueda, Jiazhen Wu, Jiang Li, Koji Horiba, Hiroshi Kumigashira, Yaoqing Zhang, and Hideo Hosono
  Phys. Rev. B, 95 (2017) 125117.
• "Ce 4f electronic states of CeO_1−xF_xBiS₂ studied by soft x-ray photoemission spectroscopy"
  Takanori Wakita, Kensei Terashima, Takahiro Hamada, Hirokazu Fujiwara, Makoto Minohara, Masaki Kobayashi, Koji Horiba, Hiroshi Kumigashira, Galif Kutluk, Masanori Nagao, Satoshi Watauchi, Isao Tanaka, Satoshi Demura, Hiroyuki Okazaki, Yoshihiko Takano, Yoshikazu Mizuguchi, Osuke Miura, Kozo Okada, Yuji Muraoka, and Takayoshi Yokoya
  Phys. Rev. B, 95 (2017) 085109.
• "Tailoring Photovoltage Response at SrRuO₃/SrTiO₃ Heterostructures"
  Ryu Yukawa, Susumu Yamamoto, Kazuma Akikubo, Kaori Takeuchi, Kenichi Ozawa, Hiroshi Kumigashira and Iwao Matsuda
  Advanced Materials Interfaces, 3 (2016) 16000527.
• "Room-temperature fabrication of light-emitting thin films based on amorphous oxide semiconductor"
  Junghwan Kim, Norihiko Miyokawa, Keisuke Ide, Yoshitake Toda, Hidenori Hiramatsu, Hideo Hosono, and Toshio Kamiya
  AIP Advances, 6 (2016) 015106.
• "Ce Core-Level Spectroscopy, and Magnetic and Electrical Transport Properties of Lightly Ce-Doped YCoO₃"
  Yoshihiko Kobayashi, Tsuyoshi Koike, Mario Okawa, Ryohei Takayanagi, Shohei Takei, Makoto Minohara, Masaki Kobayashi, Koji Horiba, Hiroshi Kumigashira, Akira Yasui, Eiji Ikenaga, Tomohiko Saitoh, and Kichizo Asai
  J. Phys. Soc. Jpn., 85 (2016) 114704.
• "Influence of k_⊥ broadening on ARPES spectra of the (110) and (001) surfaces of SrVO₃ films"
  T. Mitsuhashi, M. Minohara, R. Yukawa, M. Kitamura, K. Horiba, M. Kobayashi, and H. Kumigashira
  Phys. Rev. B, 94 (2016) 125148.
• "Thickness-dependent physical properties of La_1/3Sr_2/3FeO₃ thin films grown on SrTiO₃ (001) and (111) substrates"
  Makoto Minohara, Miho Kitamura, Hiroki Wadati, Hironori Nakao, Reiji Kumai, Youichi Murakami and Hiroshi Kumigashira
  J. Appl. Phys., 120 (2016) 025303.
• "Spatial distribution of transferred charges across the heterointerface between perovskite transition metal oxides LaNiO₃ and LaMnO₃"
  Miho Kitamura, Koji Horiba, Masaki Kobayashi, Enju Sakai, Makoto Minohara, Taichi Mitsuhashi, Atsushi Fujimori, Takuro Nagai, Hiroshi Fujioka and Hiroshi Kumigashira
  Appl. Phys. Lett., 108 (2016) 111603.
• "Isotropic Kink and Quasiparticle Excitations in the Three-Dimensional Perovskite Manganite La_0.6Sr_0.4MnO₃"
  Koji Horiba, Miho Kitamura, Kohei Yoshimatsu, Makoto Minohara, Enju Sakai, Masaki Kobayashi, Atsushi Fujimori, and Hiroshi Kumigashira
  Phys. Rev. Lett., 116 (2016) 076401.