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初貝 安弘
筑波大学
理工学群副学群長
数理物質系物理学域
筑波大学大学院
数理物質科学研究科
物理学専攻 教授
学際物質科学研究センター(TIMS)教授
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[F]  Seminar at M. Ueda Group, Univ. Tokyo, JAPAN, Jan 24 (2013)

PM1:00, Rm. 933, buld. 9, Univ. Tokyo

Title:Symmetry and order parameters for topological phases

Abstract: 
Beyond the great success of the Ginzburg-Landau theory associated with symmetry breaking (SB), condensed matter physicists focus on more than that recently. That is, phases without any fundamental SB but possessing characteristic feature are of the central interest, which are the quantum/spin liquids. This class of matter includes quite wide varieties such as quantum (spin) Hall states, gapped quantum spins, anisotropic superfluids/superconductors and graphene. Some of cold atoms and photonic systems belong to the class as well.
Even though the SB is absent, too much generic states are boring. Then still the symmetry plays an important role to constrain the physical states. Gauge symmetries, time-reversal and charge conjugation are important examples. When the quantum/spin liquid is stable against for some perturbation due to geometrical constraints, one may consider the state topological.
As for the topological phases with some symmetry protection, we can define "topological order parameter" using topological objects, such as gap nodes, quantized Berry phases and Chern numbers. Some of edge states, which are induced by geometric perturbation such as boundaries and impurities, are again topologically stable and used for the topological order parameters. This is the bulk-edge correspondence. As for the gapped cases, these topological order parameters are adiabatic invariants and useful for identification of the quantum phase transition.
We will describe generic idea of the topological phases and show validity of our topological characterization for various quantum phases.
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前
[P] MANA seminar & lectures at X. Hu Group at NIMS, Tsukuba, JAPAN, March 6 (2013)
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[P] 2013 EMN West Meeting on Topological Insulators, Houston, USA Jan 7-10(2013

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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99日!
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投稿者 : hatsugai 投稿日時: 2017-08-17 17:01:30 (201 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 (86 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 (142 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 (228 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


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    [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]
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    [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)
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    [9] ETH, Zurich (2008)
    [10] ICREA, Sant Benet (2009)
    [11] JPS Meeting, Kumamoto (2009)
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