Regensburg 2016 – scientific program

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TT: Fachverband Tiefe Temperaturen

TT 15: Focus Session: Spectroscopy of Quantum Spin Liquids

TT 15.1: Invited Talk

Monday, March 7, 2016, 15:00–15:30, H20

Thermodynamics of Fractional Quantum Spin Liquids — •Yukitoshi Motome — University of Tokyo, Tokyo, Japan

After the proposal by P. W. Anderson in 1973, the quantum spin liquid (QSL) has attracted continuous interest as a new quantum state of matter. Although several candidate materials have been synthesized, it remains elusive to prove that their low-temperature state is a QSL, mainly because of the lack of order parameters that are experimentally accessible. On the other hand, one of the salient features of QSLs is the fractionalization of quantum spins. In this contribution, we theoretically show that the fractionalized spins manifest themselves in the finite-temperature properties, in particular, in the paramagnetic state as a precursor of QSL. We address this issue in the Kitaev model and its extensions, in which the quantum spin fractionalizes into two types of Majorana fermions in the QSL ground state. By using the newly-developed quantum Monte Carlo technique in the Majorana fermion representation, we find that many experimentally-accessible quantities experience the fractionalization in their temperature dependences. We also show that, in some cases, the fractionalization causes exotic phase transitions between the three states of matter in magnets: solid (long-range ordered state), gas (paramagnet), and liquid (QSL). Our findings will be helpful as “smoking gun" experiments for QSLs.

This work has been done in collaboration with J. Nasu, M. Udagawa, Y. Kamiya, and Y. Kato.

References at www.motome-lab.t.u-tokyo.ac.jp/publication-e.html.

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