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Who am I ?
初貝 安弘 筑波大学筑波大学大学院 数理物質科学研究科 物理学専攻 教授 初貝写真
会議 & 研究会
グーグル検索:初貝
ResercherID: Y.Hatsugai
Project
メインメニュー
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サイト内新着一覧 - 記事一覧
http://rhodia.ph.tsukuba.ac.jp/~hatsugai/
発行日時 |
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2020-12-3 15:53
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研究室
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VII トポロジカル相でのバルク・エッジ対応の多様性と普遍性:固体物理を越えて分野横断へ April 2017 - March 2022
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2020-12-1 13:58
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研究室
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III. 現在の研究費と進行中のプロジェクト (2020)
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2020-12-1 13:41
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研究室
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III-p. 過去の研究費と進行中のプロジェクト (2019)
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2020-11-4 16:12
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研究室
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[F] 名古屋大学 特別講義 , Dec.14-16 (2020): hosted by Prof. Hiroshi Kohno
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2020-11-4 15:54
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研究室
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[F] 日本物理学会 2020年秋季大会 online , Sep.8-11 (2020)
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2020-11-3 10:00
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ニュース
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Thouless pump and SPT's phase boundary
Thouless' (adiabatic) pump in one-dimension is a typical topological phenomena characterized by the Chern number that correspondes to the quantized motion of the center of mass (COM). Although the COM is only well-defined with boudary (to set the origin of the coordinate), the COM experimentally observed is given by the bulk and the edge states do not contribute. Ultimate adiabaticity, that has never been achieved experimentaly, supports the quantization of the COM supplemented by the periodicity of the system with boundaries. This is the unique bulk-edge correspondence of the pump. We here propose a generic construction using a phase boundary line of the symmetry protect phase with two parameters works as a topological obstruction of the pump in extended parameter space. The construction is purely of manybody and the interaction can be one of the parameters. Have a look at "Interaction-induced topological charge pump" by Yoshihito Kuno and Yasuhiro Hatsugai, Phys. Rev. Research 2, 042024(R), (2020) (Open access)
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2020-10-28 10:28
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ニュース
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Editors' choice and News & Comm. of JPSJ: Type III Dirac cones...
The Dirac cone is a typical singular energy dispersion in two dimensions that is a source of various non-trivial topological effects. When realized in real/synthetic materials, it is generically tilted and the equi-energy surface (curve) can be elliptic/hyperbolic (type I/II). The type III Dirac cone is a critical situation between the type I and II that potentially causes various non-trivial physics. As for realization of the type III Dirac cones, we are proposing a generic theoretical scheme without any fine tuning of material parameters . It may also help to synthesize in meta materials. The molecular orbital (MO) construction of the generic flat bands which we are also proposing plays a crutial role. Have a look at "Type-III Dirac Cones from Degenerate Directionally Flat Bands: Viewpoint from Molecular-Orbital Representation" by Tomonari Mizoguchi and Yasuhiro Hatsugai, J. Phys. Soc. Jpn. 89, 103704 (2020) Also arXiv:2007.14643. The paper has been selected as an Editors' choice of J. Phys. Soc. Jpn. (Sep. 2020). See also "News and comments" by Prof. N. Nagaosa.
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2020-10-23 11:05
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研究室
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Grant-in-Aid for Scientific Research (S) Project No.17H06138, 7-th informal meeting, Oct.20, 2020 (zoom)
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2020-10-22 13:15
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研究室
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科研費基盤S第3回インフォーマル研究会 May19-20 2018
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2020-10-5 14:20
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研究室
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[P] JPS 2019 Fall meeting, Gifu, Sep. 10-13, (2019)
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2020-10-1 16:07
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ニュース
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Square-root higher order topological insulator (SR-HOTI)
Motivated by a historical example, the Dirac Hamiltonian as a square-root of the Klein-Gordon Hamiltonian, its lattice analogue has been discussed recently. Zero energy states are shared by the parent and its descendant. The story is more than that. Not necessarily zero energy but its high energy part can also share topological characters. We hereby propose a “square-root higher order topological insulator (square-root HOTI)” when its squared parent is HOTI. Based on the simple observation that square of the decorated honeycomb lattice is given by a decoupled sum of the Kagome and honeycomb lattices, we have demonstrate that the “corner states” of the breezing Kagome lattice with boundaries share topological characters with its descendant as the decorated honeycomb lattice. Have a look at our recent paper just published online, "Square-root higher-order topological insulator on a decorated honeycomb lattice" by Tomonari Mizoguchi, Yoshihito Kuno, and Yasuhiro Hatsugai, Phys. Rev. A 102, 033527 (2020), also arXiv:2004.03235.
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2020-9-18 11:42
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研究室
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連絡先
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2020-9-17 11:42
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ニュース
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Topological characterization of full Liouvillian for non-Hermitian FQH
As for a topological characterization of a full Liouvillian (including jump term) for the non hermitian fractional quantum Hall states, we are proposing a pseudospin Chern number associated with the Niu-Thouless-Wu type twists in the doubled Hilbert space. Numerical demonstration of the proposal is explicitely given and its validity is discussed. Have a look at "Fate of fractional quantum Hall states in open quantum systems: Characterization of correlated topological states for the full Liouvillian" by Tsuneya Yoshida, Koji Kudo, Hosho Katsura, and Yasuhiro Hatsugai, Phys. Rev. Research 2, 033428 (2020) (open access).
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2020-9-4 10:14
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研究室
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[F]筑波大学数学域「数理科学研究コア」「RCMSサロン」 July, 2020 (postponed due to COVID19)
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2020-8-16 14:53
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ニュース
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Adiabatic heuristic on a torus
Adiabatic deformation of gapped systems is a conceptual basis of topological phases. It implies that topological invariants of the bulk described by the Berry connection work as topological order parameters of the phase. This is independent of the well-established symmetry breaking scenario of the phase characterization. Adiabatic heuristic argument for the fractional quantum Hall states is one of the oldest such trials that states the "FRACTIONAL" state is deformed to the “INTEGER”. Although it is intuitive and physically quite natural, there exist several difficulties. How the states with different degeneracy are deformed each other adiabatically? We have clarified the questions and demonstrated this adiabatic deformation on a torus in the paper "Adiabatic heuristic principle on a torus and generalized Streda formula" by Koji Kudo and Yasuhiro Hatsugai , Phys. Rev. B 102, 125108 (2020) (also arXiv:2004.00859) What is deformed continuously is a gap not the states ! This is also sufficient for the topological stability of the Chern number (of the degenerate multiplet) as a topological order parameter. Have a look at.
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2020-7-30 12:47
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ニュース
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Review article on non-hermitian band touching
Our article on non-hermitian band touching for strongly correlated systems has been published in PTEP (Progress of Theoretical and Experimental Physics), "Exceptional band touching for strongly correlated systems in equilibrium", by Tsuneya Yoshida, Robert Peters, Norio Kawakami, Yasuhiro Hatsugai. Focusing on the non-hermitian topological phenomena for the equilibrium Green function of correlated electrons, a compact review of the exceptonal band touching that is intrinsic for non-hermitian matrices is described as well. Have a look at.
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2020-7-9 12:45
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ニュース
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Mechanical modes of Lieb lattice
Mass points on a periodic lattice connected by springs (spring-mass model) is a simple mechanical system described by an energy-momentum dispersion, that is a macroscopic phonon. We hereby discuss it on the Lieb lattice with chiral symmetry. It possesses extra degeneracy at some momentum compared with well investigated electronic systems (due to extra degree of freedoms). Have a look at "Topological Modes Protected by Chiral and Two-Fold Rotational Symmetry in a Spring-Mass Model with a Lieb Lattice Structure", J. Phys. Soc. Jpn. 89, 083702 (2020) by Hiromasa Wakao, Tsuneya Yoshida , Tomonari Mizoguchi , and Yasuhiro Hatsugai.
Also arXiv:2005.00752.
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2020-6-18 7:34
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ニュース
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Mirror skin effects for electric circuit
Linear electric circuits are one more non-quantum platform of the topological phenomena such as bulk-edge correspondence we have been working around. Then its non-hermitian extension with/without symmetry is surely of the important targets. We have here discussed mirror skin effects of the non-hermitian electric circuit where the boundary states dominate on the mirror symmetric lines. Also possible realization is proposed. Have a look at "Mirror skin effect and its electric circuit simulation" by Tsuneya Yoshida, Tomonari Mizoguchi, and Yasuhiro Hatsugai, Phys. Rev. Research 2, 022062(R) (2020) (Open access).
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2020-6-9 12:11
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ニュース
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Flat bands with non zero Chern numbers
We have been proposing a systematic construction scheme of flat bands by molecular orbitals (MO). Now it is extended for systems with non trivial topology where non trivial bands with non zero Chern numer may cross the flat bands although the Chern number of the flat band itself is vanishing. We have presented a various other examples such as the Haldane model and the Kane-Mele model of the MOs'. Have a look at Systematic construction of topological flat-band models by molecular-orbital representation" by Tomonari Mizoguchi and Yasuhiro Hatsugai, Phys. Rev. B 101, 235125 (2020) also arXiv:2001.10255.
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2020-3-15 0:55
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ニュース
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Higher order topological phases in a spring mass model
Topological phases are everywhere. Higher order topological phases are realized in a spring mass model on a Kagome lattice. Berry phases quantized in a unit of 2π/3 predict localized vibration modes near the corner of the system. This quantization is due to a symmetry protection. Have a look at our paper in Physical Review B. Most of the topological phenomena are realized in a mechanical analogue, which are much accessible without any real high-tech. Of course, it is still a non-trivial task.
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今年もやります。まずは 量子力学3(遠隔).
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令和二年の新年あけましておめでとうございます。今年もあと-1183日!
最新ニュース
投稿者 : hatsugai 投稿日時: 2020-11-03 10:00:50 ( 4760 ヒット) Thouless' (adiabatic) pump in one-dimension is a typical topological phenomena characterized by the Chern number that correspondes to the quantized motion of the center of mass (COM). Although the COM is only well-defined with boudary (to set the origin of the coordinate), the COM experimentally observed is given by the bulk and the edge states do not contribute. Ultimate adiabaticity, that has never been achieved experimentaly, supports the quantization of the COM supplemented by the periodicity of the system with boundaries. This is the unique bulk-edge correspondence of the pump. We here propose a generic construction using a phase boundary line of the symmetry protect phase with two parameters works as a topological obstruction of the pump in extended parameter space. The construction is purely of manybody and the interaction can be one of the parameters. Have a look at "Interaction-induced topological charge pump" by Yoshihito Kuno and Yasuhiro Hatsugai, Phys. Rev. Research 2, 042024(R), (2020) (Open access) 投稿者 : hatsugai 投稿日時: 2020-10-01 16:07:56 ( 5231 ヒット) Motivated by a historical example, the Dirac Hamiltonian as a square-root of the Klein-Gordon Hamiltonian, its lattice analogue has been discussed recently. Zero energy states are shared by the parent and its descendant. The story is more than that. Not necessarily zero energy but its high energy part can also share topological characters. We hereby propose a “square-root higher order topological insulator (square-root HOTI)” when its squared parent is HOTI. Based on the simple observation that square of the decorated honeycomb lattice is given by a decoupled sum of the Kagome and honeycomb lattices, we have demonstrate that the “corner states” of the breezing Kagome lattice with boundaries share topological characters with its descendant as the decorated honeycomb lattice. Have a look at our recent paper just published online, "Square-root higher-order topological insulator on a decorated honeycomb lattice" by Tomonari Mizoguchi, Yoshihito Kuno, and Yasuhiro Hatsugai, Phys. Rev. A 102, 033527 (2020), also arXiv:2004.03235. 投稿者 : hatsugai 投稿日時: 2020-08-16 14:53:28 ( 5425 ヒット) Adiabatic deformation of gapped systems is a conceptual basis of topological phases. It implies that topological invariants of the bulk described by the Berry connection work as topological order parameters of the phase. This is independent of the well-established symmetry breaking scenario of the phase characterization. Adiabatic heuristic argument for the fractional quantum Hall states is one of the oldest such trials that states the "FRACTIONAL" state is deformed to the “INTEGER”. Although it is intuitive and physically quite natural, there exist several difficulties. How the states with different degeneracy are deformed each other adiabatically? We have clarified the questions and demonstrated this adiabatic deformation on a torus in the paper "Adiabatic heuristic principle on a torus and generalized Streda formula" by Koji Kudo and Yasuhiro Hatsugai , Phys. Rev. B 102, 125108 (2020) (also arXiv:2004.00859) What is deformed continuously is a gap not the states ! This is also sufficient for the topological stability of the Chern number (of the degenerate multiplet) as a topological order parameter. Have a look at. 検索
バルク・エッジ対応
- [0] バルクとエッジ
- [1] 集中講義
- [2] 原論文と解説
- [3] トポロジカル秩序とベリー接続:日本物理学会誌 「解説」 [JPS-HP] [pdf]
- [4] "Band gap, dangling bond and spin : a physicist's viewpoint" [pdf] [Web]
トポロジカル相
[0]昔の科研費 - 科研費 1992年度:電子系スピン系におけるトポロジカル効果
- 科研費 1994年度:物性論におけるトポロジーと幾何学的位相
私の講演ファイルのいくつか- [1] MIT, Boston (2003)
- [2] APS/JPS March Meeting (2004)
- [3] JPS Fall meeting, JAPAN (2004)
- [4] APS/JPS March meeting (2005)
- [5] JPS Fall meeting (2005):Entanglement
- [6] Superclean workshop, Nasu (2006)
- [7] MPIPKS, Dresden (2006)
- [8] KEK, Tsukuba (2007)
- [9] ETH, Zurich (2008)
- [10] ICREA, Sant Benet (2009)
- [11] JPS Meeting, Kumamoto (2009)
- [12]HMF19, Fukuoka (2010)
- [13] NTU, Singapore (2011)
- [14] ICTP, Trieste (2011)
- [15] Villa conf., Orland (2012)
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