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初貝 安弘 ORCID iD icon
筑波大学
筑波大学大学院
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投稿者 : hatsugai 投稿日時: 2020-02-26 09:17:33 (845 ヒット)

Pierre Delplace (Laboratoire de Physique, École Normale Supérieure de Lyon, France) will be telling us on his series of works as a title "Topological waves from condensed matter to the atmosphere". Audience from various area is welcome such as physics and geophysics. The talk is from 14:00 Feb. 27 (2020) at B118. See details in pdf. Join us.


投稿者 : hatsugai 投稿日時: 2019-12-06 18:21:14 (921 ヒット)

On Dec. 18, 2019, Yuichi Otsuka (RIKEN) will tell us on their work of the quantum Monte Carlo study for interacting Dirac fermions on lattice. As is known, the Dirac fermions are mother of all topological phases. " QMC Study of quantum criticality in 2D interacting Dirac fermions.". The talk will be given in Japanese.


投稿者 : hatsugai 投稿日時: 2019-12-03 01:35:51 (1111 ヒット)

On Dec. 11 (Wed), K. Kawaguchi (RIKEN) will tell us on their work by a title "Collective cell dynamics and topology". It's a new area for us. Join the seminar. The talk will be given in Japanese.


投稿者 : hatsugai 投稿日時: 2019-08-26 14:24:32 (1004 ヒット)

Ryo Okugawa (WPI-AIMR, Tohoku Univ.) will be telling us on his recent work as a title "Chiral-symmetry protected second-order topological phases" on Sep. 18 (2019). Rm. D301 from 13:30pm. Join us.


投稿者 : hatsugai 投稿日時: 2019-07-27 17:21:02 (1705 ヒット)

8月8日(木)15:00から東京大学/産総研の青木秀夫先生に最近のご研究についてのセミナーをお願いいたしました。「平坦バンド模型における超伝導およびトポロジカル系の設計」。場所は自然系学系棟B棟6階602号室となっております。是非ご参加ください。


投稿者 : hatsugai 投稿日時: 2019-07-08 09:51:39 (1348 ヒット)

NTTI2019 & BEC 2019 at Hiroshima, July 14-19 (2019) is coming. We have organized a series of international workshops BEC2015, 2016, 2018, 2018X. This year, we have a joint international workshop with NTTI as NTTI2019 & BEC2019 at Hiroshima. Join us.


投稿者 : hatsugai 投稿日時: 2019-06-11 16:12:43 (1236 ヒット)

Jyong-Hao Chen (ETH, PSI & ISSP) will be telling us on his recent work as a title "Model of spin liquids with Abelian and non-Abelian topological phases" on June 19 (2019). Rm. D301 from 13:30pm. Join us.


投稿者 : hatsugai 投稿日時: 2019-04-24 17:39:37 (1524 ヒット)

Shintaro Hoshino will be telling us about "Spectral bulk-boundary correspondence and topological criticality in chiral-symmetric superconductors" on May 15 (2019). Join us.


投稿者 : hatsugai 投稿日時: 2018-12-06 22:57:18 (2173 ヒット)

Yuji Matsuda (Kyoto Univ.) will be telling us about their discoveries on Dec. 14 entitled as "Majorana fermions and half-integer thermal quantum Hall effect in a quantum spin liquid". Its detail is here. Join us !


投稿者 : hatsugai 投稿日時: 2018-12-05 17:03:35 (1572 ヒット)

Nobuyuki Okuma (Kyoto Univ.) will tell us in a long seminar entitled as "Real-Space Topological Classification: Higher-order topology and Atiyah-Hirzebruch spectral sequence" on Dec.19. The detail is here. Join us.


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今年もやります。まずは量子力学3(遠隔). 冬は 統計力学2 改め物性理論II (大学院「ベリー接続の理論とバルクエッジ対応」). 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33日!
最新ニュース
投稿者 : hatsugai 投稿日時: 2020-11-03 10:00:50 (97 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: 2020-10-28 10:28:43 (245 ヒット)

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.


投稿者 : hatsugai 投稿日時: 2020-10-01 16:07:56 (297 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: 2020-09-17 11:42:01 (171 ヒット)

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).


投稿者 : hatsugai 投稿日時: 2020-08-16 14:53:28 (350 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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