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初貝 安弘 ORCID iD icon
筑波大学
筑波大学大学院
数理物質科学研究科
物理学専攻 教授
初貝写真
Yasuhiro2-Nov11-09
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ResercherID: Y.Hatsugai
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メインメニュー
Date:May 27, 2010
Title:
Many-body effects on the optical and magnetic properties of doped graphene sheets
Speaker:
Prof. Giovanni Vignale, (University of Missouri)
Room & time:
D312, 15:00-16:00
Abstract:
I report on the results of our recent investigations of many-body effects in doped graphene sheets. First, we have calculated the first-order interaction corrections to the Drude weight, plasmon dispersion, and optical response of this system. We find that, due to the lack of Galilean invariance, both the plasmon frequency and the Drude weight are enhanced relative to the RPA value. This effect is due to the coupling between the center of mass motion and the pseudo-spin degree of freedom of the massless Dirac fermions. We then apply similar many-body theoretical methods to the calculation of the orbital magnetic susceptibility of a gas of interacting massless Dirac fermions. This susceptibility is zero in the absence of interactions, when the Fermi energy is away from the Dirac point. Our perturbative calculations show that first-order interaction corrections to the orbital magnetic susceptibility are finite and positive. Doped graphene sheets are thus unique systems in which the orbital susceptibility is completely controlled by many-body effects, leading to orbital paramagnetism.
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宇田川将文 氏「電荷アイスの量子融解と非フェルミ液体的挙動」 July13, 2010

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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4 (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178日!
最新ニュース
投稿者 : hatsugai 投稿日時: 2020-06-18 07:34:20 (69 ヒット)

Linear electric circuits are one more non-quantum platform of the topological phenomena such as bulk-edge correspondence we have been working around. Then its non-hermitian extension with/without symmetry is surely of the important targets. We have here discussed mirror skin effects of the non-hermitian electric circuit where the boundary states dominate on the mirror symmetric lines. Also possible realization is proposed. Have a look at "Mirror skin effect and its electric circuit simulation" by Tsuneya Yoshida, Tomonari Mizoguchi, and Yasuhiro Hatsugai, Phys. Rev. Research 2, 022062(R) (2020) (Open access).


投稿者 : hatsugai 投稿日時: 2020-06-09 12:11:19 (88 ヒット)

We have been proposing a systematic construction scheme of flat bands by molecular orbitals (MO). Now it is extended for systems with non trivial topology where non trivial bands with non zero Chern numer may cross the flat bands although the Chern number of the flat band itself is vanishing. We have presented a various other examples such as the Haldane model and the Kane-Mele model of the MOs'. Have a look at Systematic construction of topological flat-band models by molecular-orbital representation" by Tomonari Mizoguchi and Yasuhiro Hatsugai, Phys. Rev. B 101, 235125 (2020) also arXiv:2001.10255.


投稿者 : hatsugai 投稿日時: 2020-03-15 00:55:42 (270 ヒット)

Topological phases are everywhere. Higher order topological phases are realized in a spring mass model on a Kagome lattice. Berry phases quantized in a unit of 2π/3 predict localized vibration modes near the corner of the system. This quantization is due to a symmetry protection. Have a look at our paper in Physical Review B. Most of the topological phenomena are realized in a mechanical analogue, which are much accessible without any real high-tech. Of course, it is still a non-trivial task.


投稿者 : hatsugai 投稿日時: 2020-02-26 09:17:33 (401 ヒット)

Pierre Delplace (Laboratoire de Physique, École Normale Supérieure de Lyon, France) will be telling us on his series of works as a title "Topological waves from condensed matter to the atmosphere". Audience from various area is welcome such as physics and geophysics. The talk is from 14:00 Feb. 27 (2020) at B118. See details in pdf. Join us.


投稿者 : hatsugai 投稿日時: 2020-01-15 01:17:36 (519 ヒット)

ZQ Berry phase, that is quantized due to symmetry, is defined and used successfully for characterization of 2D/3D higher order topological phases with/without interaction. Both for spins and fermions. The article by Hiromu Araki, Tomonari Mizoguchi and Yasuhiro Hatsugai has been published in Physical Review Research. Also it is highlighted here as one of the Rapid Communications. Have a look at !


    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
    私の講演ファイルのいくつか
    [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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