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14:00-15:30, Tuesday, Oct. 13, 2020

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ZOOM webinar, please sign up by scanning QR Code for participation

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Faculty and Staff,Graduate Students,Undergraduate Students

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Academics and Research

Physics Colloquium | Yuji Matsuda: Half-Integer Quantized Thermal Hall Effect in the Kitaev Quantum Spin Liquid

Speaker:Yuji Matsuda, Department of Physics, Kyoto University, Sakyo-ku, Kyoto, Japan


Yuji Matsuda obtained his Ph.D. from the Department of Physics, the University of Tokyo (1987). He was a research associate at the University of Tokyo, a postdoctoral fellow at Princeton University, an associate professor at Hokkaido University and the University of Tokyo. He has been a full professor at Department of Physics, Kyoto University, since 2004. His current research interests include strongly correlated electron systems, in particular unconvensional superconductivity and quantum spin systems. He received Nishina memorial award, Kamerlingh Onnes prize, and award of Science and technology from the Minister of Education, Culture, Sports Science and Technology.


Title:

Half-integer quantized thermal Hall effect in the Kitaev quantum spin liquid


Abstract:

When topology is combined with strong correlations, fascinating phenomena can arise, such as the emergence of collective excitations having fractional quantum numbers with respect to the elementary particles. One of the most prominent examples is the fractional QHE, in which the constituent particles are electrons but the quasiparticles carry fractions of the electron charge. Another venue for the interplay of topology and correlations are quantum spin liquids in magnetic insulators.


A paradigmatic example is the Kitaev spin liquid, which forms for strongly interacting spins in a magnetic field and exhibits anyonic quasiparticles in the form of massive Z2 vortices that bind a Majorana zero mode. The non-Abelian character of these Ising anyons in the Kitaev spin liquid is identical to that of certain topological superconductors and the n=5/2 fractional quantum Hall state. Direct experimental evidence for the formation of a topological state with non-Abelian anyons has long been sought-after. In fact, it required the observation of yet another QHE -- a quantized thermal Hall effect.


Recently a half-integer thermal quantum Hall conductance has been reported for the 2D honeycomb magnet a-RuCl3[1]. The field-angular variation of the quantized thermal Hall conductance has the same sign structure of the topological Chern number, which is either +1 or -1, as the Majorana band structure of the pure Kitaev spin liquid. This observation of a half-integer anomalous thermal Hall effect firmly establishes that the non-Abelian topological order associated with fractionalization of the local magnetic moments persists even in the presence of non-Kitaev interactions in a-RuCl3 [2].


Reference

[1] Y. Kasahara et al., Nature 559, 227 (2018).

[2] T. Yokoi et al. arXiv:2001.01899.


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Contact:

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Time & Date

14:00-15:30, Tuesday, Oct. 13, 2020

Venue

ZOOM webinar, please sign up by scanning QR Code for participation

Host

Audience

Faculty and Staff,Graduate Students,Undergraduate Students

Category

Academics and Research