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HATSUGAI   Lab.     Institute of Physics, University of Tsukuba


L: Topological stability of Dirac cones, merging & C: fractal in graphene (Flying Butterfly) & R: Non Abelian gauge structure in solids
Refereneces :
[1] Y. Hatsugai, T. Fukui, H. Aoki, Phys. Rev. B 74, 205414 (2006) : [Journal Link] , arXiv:cond-mat/0607669
"Topological analysis of the quantum Hall effect in graphene"
[2] Y. Hatsugai, J. Phys. Soc. Jpn. 73, 2604 (2004) : [Journal Link] , arXiv:cond-mat/0405551
"Explicit Gauge Fixing for Degenerate Multiplets: A Generic Setup for Topological Orders"

Hatsugai Group, Condensed Matter Theory

Targets of our research is to explore new insight and find novel physical principles in condensed matter materials and phenomena. We have been working on the following topics. [paper]

[1] Geometrical phases of condensed matter physics
Target material and phenomena
(1) Graphene as a relativistic Dirac particle in solid states
(2) Quantum Hall effects as typical topological insulators
(3) Quantum spin Hall phase as a time reversal invariant topological insulator
(4) Electrons with strong correlation as non trivial quantum liquids
(5) Exotic superconductivity with anisotropic pairing
(6) Frustrated magnets as typical spin liquids
(7) Semiconductor nano-structures as a playground of novel quantum phenomena
(8) Universal edge states in quantum (spin) Hall effects, Haldane magnets, photonic crystals and cold atoms
(9) Aharonov-Bohm effect and its generalization

Theoretical methods and concepts
(1) Non-Abelian gauge structures of the Berry connections
(2) Berry connections and their generalization
(3) Quantum order parameters by the Chern numbers and generic Berry phases
(4) Theory of generic Aharnov-Bohm effects
(5) Entanglement entropy of quantum liquids and spin liquids
(6) Universality of the Bulk-Edge correspondence
(7) Characterization of topological orders in quantum liquids


[2] Novel quantum phenomena in real material and their relation to the emerging mathematical concepts as quantum group
Some works [Link1][Link2]
[3] Novel techniques to study ferimonic many body systems with strong correlation
Basic work [Link]
[4] Realistic electronic structures & topological quantities
One of my basic works [Link]


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  • Graduate courses at Univ. of Tsukuba [Web]
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Institute of Physics
University of Tsukuba
1-1-1 Tennodai
Tsukuba
Ibaraki 305-8571
JAPAN


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Year 2013
A HAPPY NEW YEAR 2019, 25 days left this year !
Recent News
Poster : hatsugai on 2019-12-06 18:21:14 (9 reads)

On Dec. 18, 2019, Yuichi Otsuka (RIKEN) will tell us on their work of the quantum Monte Carlo study for interacting Dirac fermions on lattice. As is known, the Dirac fermions are mother of all topological phases. " QMC Study of quantum criticality in 2D interacting Dirac fermions.". The talk will be given in Japanese.


Poster : hatsugai on 2019-12-03 01:35:51 (70 reads)

On Dec. 11 (Wed), K. Kawaguchi (RIKEN) will tell us on their work by a title "Collective cell dynamics and topology". It's a new area for us. Join the seminar. The talk will be given in Japanese.


Poster : hatsugai on 2019-11-18 18:54:05 (81 reads)

We have discussed a non-hermitian version of the fractional quantum Hall states. The paper, by Tsuneya Yoshida, Koji Kudo and Yasuhiro Hatsugai, has been published in Scientific Reports ( also arXiv:1907.07596 ). Non-hermitian physics has been extended to the topologically ordered states. It's a try. Relevant situations can be realized in cold atom experiments.


Poster : hatsugai on 2019-11-14 01:28:29 (114 reads)

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).


Poster : hatsugai on 2019-11-09 07:50:55 (240 reads)

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.


    Search
    Bulk-edge correspondence
    [0] バルクとエッジ
    [1] Focus lecture
    [2] Original papers
    [3] Japanese Physical Society monthly issue Commentary (Only Japanese except abstract) [pdf]
    [4] "Band gap, dangling bond and spin : a physicist's viewpoint" [pdf]
    Topological phases
    [0]Historical project
    KAKEN-HI DB FY1992 : Topological effects in electronic/spin systems
    KAKEN-HI DB FY1994 : Topology & geometrical phases in condensed matter physics
    Some of my talk files
    [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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