物性物理学/物性理論初貝研究室/筑波大学 - メニュー

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筑波大学
筑波大学大学院
数理物質科学研究科
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ホーム研究室研究教育メンバ－セミナー大学院入学希望者へアクセス写真 Web 記事最近の更新サイトマップニュース

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2011.3.11の震災で大きな被害を受けられた皆様にお見舞い申し上げます。日本頑張れ！　　ようこそ、初貝研究室へ　

初貝研究室筑波大学大学院数理物質科学研究科物理学専攻

L: トポロジカルに安定なディラックコーンとその融合& C:「グラフェン中のフラクタル」(Flying Butterfly：蝶が飛んでるようにみえませんか？) & R: 「固体物質中の非可換ゲージ構造」参考文献：

[1] Y. Hatsugai, T. Fukui, H. Aoki, Phys. Rev. B 74, 205414 (2006) : [Journal Link] , arXiv:cond-mat/0607669: "Topological analysis of the quantum Hall effect in graphene"
[2] Y. Hatsugai, J. Phys. Soc. Jpn. 73, 2604 (2004) : [Journal Link] , arXiv:cond-mat/0405551: "Explicit Gauge Fixing for Degenerate Multiplets: A Generic Setup for Topological Orders"

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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-883日！

最新ニュース

ニュース!! : Thouless pump and SPT's phase boundary

投稿者 : hatsugai 投稿日時： 2020-11-03 10:00:50 (3479 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)

ニュース!! : Editors' choice and News & Comm. of JPSJ: Type III Dirac cones...

投稿者 : hatsugai 投稿日時： 2020-10-28 10:28:43 (4359 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.

ニュース!! : Square-root higher order topological insulator (SR-HOTI)

投稿者 : hatsugai 投稿日時： 2020-10-01 16:07:56 (3774 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.

ニュース!! : Topological characterization of full Liouvillian for non-Hermitian FQH

投稿者 : hatsugai 投稿日時： 2020-09-17 11:42:01 (3754 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).

ニュース!! : Adiabatic heuristic on a torus

投稿者 : hatsugai 投稿日時： 2020-08-16 14:53:28 (4012 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

高度な検索

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

[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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研究解説: (21)
- グラフェン(3)
- 量子液体(9)
- ベリー接続(9)
その他：高校生、学部学生向け(5)

最新のエントリ

原点(2019-3-13 6:36)
久しぶりにグラフェンとは？(2013-9-16 23:19)
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平成23年度筑波大学理工学群物理学類学位授与式物理学類長祝辞(2012-4-5 10:29)
物理学はじめの一歩 (2011-4-25 11:46)
2次元と３次元でぐるぐる(2010-8-20 0:40)
クラマース縮退と四元数的ベリー接続(2010-7-6 10:19)

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