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アルバムトップ : 私たち : 初貝 :  Yasuhiro2-Nov11-09

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投稿者hatsugaihatsugai さんの画像をもっと!   前回更新2009-11-20 14:38    
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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31年の新年あけましておめでとうございます。今年もあと44日!
投稿者 : hatsugai 投稿日時: 2019-11-14 01:28:29 (79 ヒット)

Covalent Organic Frameworks (COF), I understand, is a large molecule where many (block) organic molecules are linked by strong covalent bonds in a periodic or non-periodic manner. It is a nice place where the higher order topological insulating phase is realized as we have pointed out. Then if the COF has boundaries, one can naturally expect edge states/corner states associated with the symmetry protected Berry phases of the bulk. This is correct. One of such a COF, we discussed, is a polymerized triptycene on a decorated star lattice. Our paper ”Flat bands and higher-order topology in polymerized triptycene: Tight-binding analysis on decorated star lattices” by Tomonari Mizoguchi, Mina Maruyama, Susumu Okada, Yasuhiro Hatsugai is for the phenomena and has been published in Physical Review Materials (See also arXiv 1907.06088).

投稿者 : hatsugai 投稿日時: 2019-11-09 07:50:55 (172 ヒット)

We have proposed a new correlated topological phase, "higher-order topological Mott insulator (HOTMI)" where spin-charge separated corner states emerge that are protected by Z3 spin Berry phases of the bulk. It is a generalized bulk-edge correspondence. The article has been published in Phys. Rev. Lett. (also arXiv:1905.03484). Have a look at.

投稿者 : hatsugai 投稿日時: 2019-09-30 11:19:28 (229 ヒット)

Exact flatness of energy bands implies some reasons behind. Here we present one of them, "molecular orbital (MO) representation", which seems to be applied for various classes of tight binding models. Mathematically if the rank of the hamiltonian as a linear operator is less than the number of atomic sites, the kernel of the linear operator has a finite dimension. This is the zero mode flat band. The MO rep. presents nice physical reasons for it. Original proposal by YH with Isao Maruyama in 2011 in EPL and arXiv is counting dimensions of non-orthogonal projections but the hopping of the MO's is allowed as we pointed out (it should be). It's a fun to guess what kinds of the MO representation is possible for a known flat band system. Try ! Also several physical reason why the flat band crosses/touches to dispersive bands in many cases are discussed. Our new paper has appeared in EPL, "Molecular-orbital representation of generic flat-band models", by T. Mizoguchi and Y. Hatsugai , also arXiv.

投稿者 : hatsugai 投稿日時: 2019-09-10 11:03:57 (188 ヒット)

I wrote a small article "So Small Implies So Large: For a Material Design" in the "News and comment" section of the JPSJ in relation to a recent interesting paper by Toshikaze Kariyado. Material deformation induces a gauge field that modifies electronic structure and may result in the Landau levels without breaking time reversal. Have a look at.

投稿者 : hatsugai 投稿日時: 2019-09-09 22:11:58 (186 ヒット)

Our paper "Higher-Order Topological Phase in a Honeycomb-Lattice Model with Anti-Kekulé Distortion" by Tomonari Mizoguchi, Hiromu Araki, and Yasuhiro Hatsugai, has appeared in J. Phys. Soc. Jpn. 88, 104703 (2019). One can access also via arXiv:1906.07928. Z6 quantization in honeycomb structure is the key. 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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