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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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Yasuhiro2-Nov11-09
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投稿者 : hatsugai 投稿日時: 2017-03-28 08:30:34 (7231 ヒット)

原子層科学 理論班の研究 のFacebook記事に 「傾いたり質量を持ったりするディラック粒子」 として寄稿しました。(原稿、含む英語版).原子層科学Facebookページはこちら"Tilted Dirac cones" in a facebook article of atomic layer project.


投稿者 : hatsugai 投稿日時: 2017-03-11 08:51:14 (8315 ヒット)

数学セミナー4月号, 36(2017)に2016年のノーベル物理学賞についての記事を書きました。「物質中に普遍的に存在するトポロジカルな構造」ご興味のある方はご覧ください。 日本評論社

(補足:記事中の写真の並びと名前がずれてることに校正時に気づきませんでした。左からHaldane, Kosterlitz, Thoulessの3氏です。おわびの上訂正いたします。)


投稿者 : hatsugai 投稿日時: 2016-12-28 12:07:44 (6969 ヒット)

We have extended the chiral symmetry to the case with tiled Dirac fermions on lattice. The paper is published in Phys. Rev. B 94, 235307 (2016)


投稿者 : hatsugai 投稿日時: 2016-12-12 13:50:23 (6369 ヒット)

Koji Kudo got a poster prize at the workshop in Kobe 2016. Congratulation !


投稿者 : hatsugai 投稿日時: 2016-12-07 09:59:47 (7400 ヒット)

日本物理学会 会誌 12月号(2016)の学界ニュースに2016年のノーベル物理学賞(トポロジカル相転移とトポロジカルな物質相)の解説を書きました。 [日本物理学会 会誌最新号目次] 日本物理学会会員の方はマイページよりご覧ください。


投稿者 : hatsugai 投稿日時: 2016-12-01 17:22:36 (7980 ヒット)

雑誌 パリティに2016年のノーベル物理学賞についての解説の依頼原稿を書きました。  パリティ(丸善):2016年ノーベル物理学賞:物質をトポロジカルにみる


投稿者 : hatsugai 投稿日時: 2016-12-01 16:41:58 (6447 ヒット)

1 千葉市科学館 平成 28 年度 「大人が楽しむ科学教室 ~量子力学シリーズ~」12月4日(日)(4)「トポロジカル物質の母としてのグラフェン」

2 千葉市科学館 平成 28 年度 「大人が楽しむ科学教室 ~量子力学シリーズ~」12月17日(土)(7)「物理学における対称性の役割とトポロジカル相」


投稿者 : hatsugai 投稿日時: 2016-09-16 10:55:24 (6909 ヒット)

Our paper on a photonic system in 3D which has the Weyl points due to breaking inversion is published in Phys. Rev. B as an edtors' suggestsion. See also highlights. The Weyl points are characterized as the topopoligical critial points of the sliced 2D system which has a non trivial Chern number (section Chern number) with jumps. Momentum selective edge states propagating near the boundaries are discussed as a typical example of the bulk-edge correspondence. Have a look at !


投稿者 : hatsugai 投稿日時: 2016-05-12 09:29:05 (10453 ヒット)

We are organizing a workshop on the bulk-edge correspondence in relation to cold atoms and ARPES ( theories as well) as a YITP workshop ( Yukawa Institute of theoretical physics) in Kyoto Sep.27-30, 2016. Its registration will be open soon. Stay tuned. [YITP site] . [Direct link].


投稿者 : hatsugai 投稿日時: 2016-01-16 17:16:48 (9264 ヒット)

Topological pump, proposal by Thouless and just recently realized experimeatally in Kyoto and Munich independently, is revisited from the bulk-edge correspondence (BEC). It's typically described by well known Harper equation as in QHE but the view point of BEC supplies quite different physical / mathematical structure. Pumped charge is carried by bulk but its quantization is guaranteed by the topological number defined by a singular motion of the center of mass caused by edge states. However this singular motion can not be observed in reality by a pumping of finite speed.The edge states are hidden! Counting the topological number by singularities of the spectral flow is a standard technique in the discussion of the Atiyah-Patodii-Singer index theorem. The same counting appears in the BEC in the pumping. It's a unexpected surprise. Have a look at arXiv:1601.03537, Phys. Rev. B94, 041102(R) (2016)


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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-1183日!
最新ニュース
投稿者 : hatsugai 投稿日時: 2020-11-03 10:00:50 (4759 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 (5877 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 (5229 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 (4978 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 (5422 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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