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The quantum spin liquid is an exotic quantum state of matter in magnets, where conventional symmetry breaking is prevented down to the lowest temperature by strong quantum fluctuations. It has attracted interest from not only condensed matter physics but also quantum information, owing to the anticipated topological properties. In order to clarify the nature of the enigmatic state and explore its realization, we investigate thermodynamic properties of the Kitaev model and its variants, in which the exact solutions prove the quantum spin liquids in the ground state. We will discuss the surprisingly rich behaviors of quantum spin liquids revealed by our numerical simulations, including (i) thermal fractionalization of quantum spins into Majorana fermions, (ii) ``liquid-gas" transition by proliferation of loops of excited fluxes, and (iii) phase diagram of ``magnetic three states of matter".

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Yukitoshi Motome, University of Tokyo
Seminar Room of the Institute of Physics II
Contact: Simon Trebst