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Who am I ?
Yasuhiro Hatsugai
Associate Provost (School of Science and Engineering)

Professor of Physics
Division of Physics
Faculty of Pure and Applied Sciences
TIMS Member
University of Tsukuba
1-1-1 Tennodai, Tsukuba
Ibaraki 305-8571 JAPAN
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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]


Let me explain what we are interested in!
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Information about the courses & theses. Japanese only at a moment
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Information to join us:

  • Graduate courses at Univ. of Tsukuba [Web]
  • Contact me before taking the exam !

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Institute of Physics
University of Tsukuba
1-1-1 Tennodai
Ibaraki 305-8571

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Year 2013
A HAPPY NEW YEAR 2015, 186 days left this year !
Recent News
Poster : hatsugai on 2016-05-12 09:29:05 (114 reads)

We are organizing a workshop on the bulk-edge correspondence in relation to cold atoms and ARPES ( theories as well) as a YITP workshop ( Yukawa Institute of theoretical physics) in Kyoto Sep.27-30, 2016. Its registration will be open soon. Stay tuned. [YITP site] . [Direct link].

Poster : hatsugai on 2016-01-16 17:16:48 (210 reads)

Topological pump, proposal by Thouless and just recently realized experimeatally in Kyoto and Munich independently, is revisited from the bulk-edge correspondence (BEC). It's typically described by well known Harper equation as in QHE but the view point of BEC supplies quite different physical / mathematical structure. Pumped charge is carried by bulk but its quantization is guaranteed by the topological number defined by a singular motion of the center of mass caused by edge states. However this singular motion can not be observed in reality by a pumping of finite speed.The edge states are hidden! Counting the topological number by singularities of the spectral flow is a standard technique in the discussion of the Atiyah-Patodii-Singer index theorem. The same counting appears in the BEC in the pumping. It's a unexpected surprise. Have a look at arXiv:1601.03537

Poster : hatsugai on 2016-01-16 17:16:20 (533 reads)

Our paper is now online. Topology is not only for quantum world. Localised modes near the system boundaries also exist in a classical system that is predicted by bulk. This is the bulk-edge correspondence originally discussed in quantum systems such as quantum (spin) Hall states and graphene. Still this idea is valid in classical world. We discussed topological phenomena in mechanics for point particles connected with springs in a honeycomb shape. Also topological phase transitions associated with its tension is clearly demonstrated as a time evolution of the localized modes. [arXiv:1505.06679]

    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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