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ResercherID: Y. Hatsugai
[F]  2013 EMN West Meeting on Topological Insulators,  Houston, USA  Jan 7-10(2013) [ Web ]

Invited: "Symmetry protection in topological phases"
             Yasuhiro Hatsugai
One of the characteristic features of topological phases such as topological insulators is absence of the fundamental symmetry breaking which has been a basic concept in the description of conventional order. Still symmetry plays a central role for the topological phases as symmetry protection in several ways. Gapless node structure of anisotropic superconductors is topologically protected, which is a historical example [1,2]. Generically the symmetry governs the gapless phases with massless Dirac fermions in 2D, 3D and more [3,4] where the co-dimenison of the generic degeneracy is crucial. For the gapped phases, the symmetry again controls properties of the topological systems. In addition to the intrinsically quantized quantities such as the Chern numbers, one further has adiabatic invariants by symmetry protected quantization as the Z2 Berry phases and its generalization [4,5,6]. They are used as the topological order parameters. Specifically for the topological insulators, the time reversal symmetry (TR) and the associated Kramers (KR) degeneracy are fundamentally important. Then the natural tool for the description is a quaternion and the quaternionic Berry connections of the KR pair. Topological quantities with/without TR symmetry are described in a parallel way for the Chern numbers and symmetry protected quantized quantities [5]. Also the charge-flux duality of some 3D topological insulator on a frustrated lattice will be discussed [7].
1. E. I. Blount, Phys. Rev. B 32, 2935 (1985).
2. G. E. Volovik, JETP Lett. 66, 522 (1997).
3. M. Creutz, JHEP 04, 017 (2008).
4. Y. Hatsugai, J. Phys. Soc. Japan 75, 123601 (2006).
5. Y. Hatsugai, New J. Phys. 12, 065004 (2010).
6. Y. Hatsugai and I. Maruyama, EPL 95, 20003 (2011).
7. Y. Hatsugai and Y. Avishai, to be published.
[P] Seminar at M. Ueda Group, Univ. Tokyo, JAPAN, Jan 24 (2013)
[P] Topological states of matter, Aspen, USA Jan 13--18 (2013)

今年もやります。まずは量子力学3. 冬は 統計力学2. 平成29年の新年あけましておめでとうございます。今年もあと101日!
投稿者 : hatsugai 投稿日時: 2017-08-17 17:01:30 (197 ヒット)

初貝研究室では今回助教2名を公募いたします(公募締め切り2017年9月15日)。委細は [助教公募] をご確認ください。適任者のご推薦、ご応募の方よろしくお願いいたします。

投稿者 : hatsugai 投稿日時: 2017-08-17 17:00:09 (84 ヒット)

We are organizing a Japan-Swiss workshop TTCM2017 at EPOCHAL Tsukuba, Sep.10-13 (2017). Limited number of posters will be still accepted.

投稿者 : hatsugai 投稿日時: 2017-08-03 13:38:17 (140 ヒット)

A numerical scheme to calculate the many body Chern number for a ground state multiplet is formulated and explicitly given for projected bands of any lattice. We demonstrate its validity for lattice analogue of the nu=1/3 and 1/2 states. The string gauge to realize the minimum flux compatible with the periodicity of the unit cell is also presented. [arXiv:1707.06722]. The paper is published in JPSJ lett.

投稿者 : hatsugai 投稿日時: 2017-04-21 19:57:50 (227 ヒット)

数理科学5 月号(2017年)に「物理学における線形代数:量子力学での展開」として小話を3つ書きました。1.量子もつれ, 2.平坦バンド, 3. ベリー接続としての単磁極.興味のある方はご覧ください.「物理学と数学のつながり」数理科学 5月号

    [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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