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ResercherID: Y.Hatsugai
投稿者 : hatsugai 投稿日時: 2019-06-24 12:14:01 (7884 ヒット)

物性理論(トポロジカル相の理論的または数値的研究, 量子系または古典系のバルクエッジ対応等)助教1名。 [♥ 詳細PDF] 。 応募締め切り 2019年8月31日(土)。電子メールにて応募。関係者まで周知頂けますと幸いです

投稿者 : hatsugai 投稿日時: 2017-07-04 18:51:28 (3268 ヒット)


2017年7月1日 関係機関各位


守友 浩

前略 本専攻では,下記の要領で専任教員を公募することになりました。つきましては,貴機関関係各位にご周知いただくとともに,適任者のご推薦または応募についてご配慮いただきますようお願い申し上げます.草々

公募人員: 助教2名(助教A,助教B)
所属組織: 数理物質系・物理学域
担当教育 組織:助教A:数理物質科学研究科物理学専攻, 理工学群物理学類
担当教育 組織:助教B:数理物質科学研究科物理学専攻
専門分野: 物性理論(トポロジカル相の理論)
応募資格: 博士号取得あるいは着任までに取得見込み
着任時期: 2018年4月1日,もしくは決定後できるだけ早く
雇用条件等: 裁量労働制。国家公務員共済組合に加入。雇用保険が適用。
助教B:基本年俸表適用職員。任期:単年度更新,ただし平成33年度末まで更新可能。科学研究費補助金基盤研究S (17H06138)「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」(研究代表者:初貝安弘)に関して,初貝安弘教授と協力して理論的研究を行う。本研究費による雇用。給与は筑波大学の規則に従う。

  1.  履歴書
  2.  業績リスト
  3.  主要論文別刷2編程度
  4.  今までの研究概要(2,000字程度)
  5.  着任後の研究計画と教育に関する抱負(2,000字程度)
  6.  本人について照会可能者2名以上の氏名,連絡先, または推薦書1通.推薦書は厳封の上応募書類に同封するか,直接以下の送付先に「○○氏推薦書在中」として送付。
  7.  助教Aもしくは助教Bの一方に応募、または併願を明示すること。併願の場合書類は一式でよい。

公募締切り: 2017年9月15日(金)必着
書類送付先: 〒305-8571 つくば市天王台1-1-1 筑波大学大学院 数理物質科学研究科 物理学専攻長 守友 浩
問合せ先: 同専攻 初貝安弘 

その他: 封筒に「物性理論助教応募書類在中」と朱書し,簡易書留にて送付のこと。また,応募書類は返還しない。

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37日!
投稿者 : hatsugai 投稿日時: 2020-11-03 10:00:50 (81 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 (219 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 (275 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 (152 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 (334 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.

    [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]
    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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