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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
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ResercherID: Y.Hatsugai
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2020918 11:42

研究室

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2020917 11:42

ニュース

Topological characterization of full Liouvillian for nonHermitian 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 NiuThoulessWu 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).

2020917 11:06

ニュース

Type III Dirac cones without fine tuning
The Dirac cone is a typical singular energy dispersion in two dimensions that is a source of various nontrivial topological effects. When realized in real/synthetic materials, it is generically tilted and the equienergy 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 nontrivial 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 "TypeIII Dirac Cones from Degenerate Directionally Flat Bands: Viewpoint from MolecularOrbital Representation" by Tomonari Mizoguchi and Yasuhiro Hatsugai, J. Phys. Soc. Jpn. 89, 103704 (2020) Also arXiv:2007.14643.

202098 20:05

ニュース

Squareroot higher order topological insulator (SRHOTI)
Motivated by a historical example, the Dirac Hamiltonian as a squareroot of the KleinGordon 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 “squareroot higher order topological insulator (squareroot 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, "Squareroot higherorder topological insulator on a decorated honeycomb lattice" by Tomonari Mizoguchi, Yoshihito Kuno, and Yasuhiro Hatsugai, to appear in Phys. Rev. A, also arXiv:2004.03235.

202094 10:17

研究室

[F] 日本物理学会 2020年秋季大会 online , Sep.811 (2020)

202094 10:14

研究室

[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)

202094 10:13

研究室

[F] Frontiers in higherorder topological matter, May57, NORDITA, Stockholm (postponed due to COVID19)

202094 10:09

研究室

[F] Localization2020, online, Aug.2428 (2020)

2020816 14:53

ニュース

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 wellestablished 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.

2020730 12:47

ニュース

Review article on nonhermitian band touching
Our article on nonhermitian 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 nonhermitian topological phenomena for the equilibrium Green function of correlated electrons, a compact review of the exceptonal band touching that is intrinsic for nonhermitian matrices is described as well. Have a look at.


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現在の時刻
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4 (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102日！
最新ニュース
投稿者 : hatsugai 投稿日時： 20200908 20:05:59 ( 44 ヒット) Motivated by a historical example, the Dirac Hamiltonian as a squareroot of the KleinGordon 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 “squareroot higher order topological insulator (squareroot 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, "Squareroot higherorder topological insulator on a decorated honeycomb lattice" by Tomonari Mizoguchi, Yoshihito Kuno, and Yasuhiro Hatsugai, to appear in Phys. Rev. A, also arXiv:2004.03235. 投稿者 : hatsugai 投稿日時： 20200816 14:53:28 ( 171 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 wellestablished 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」 [JPSHP] [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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