Spin correlation and Majorana spectrum in chiral spin liquids in a decorated-honeycomb Kitaev model

TMU International Symposium on "New Quantum Phases Emerging from Novel Crystal Structure"

Nasu, Joji^1 ; Motome, Yukitoshi^2

Department of Physics, Tokyo Institute of Technology, Ookayama, 2-12-1, Meguro, Tokyo

152-8551, Japan^1

Department of Applied Physics, University of Tokyo, Hongo, 7-3-1, Bunkyo, Tokyo

113-8656, Japan^2

关键词: Critical temperatures;    Crossover temperature;    Excitation spectrum;    Quantum Monte Carlo simulations;    Quantum spin models;    Temperature evolution;    Thermal fluctuations;    Time reversal symmetries;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/683/1/012037/pdf
DOI  :  10.1088/1742-6596/683/1/012037

来源: IOP

【 摘 要 】

Temperature evolution of the spin correlation and excitation spectrum is investigated for the Kitaev model defined on a decorated honeycomb lattice by using the quantum Monte Carlo simulation in the Majorana fermion representation. The ground state of this quantum spin model is given by two kinds of chiral spin liquids: one is topologically trivial with Abelian anyon excitations, and the other is topologically nontrivial with non-Abelian anyon excitations. While lowering temperature, the model exhibits several crossovers in the paramagnetic state, which originate from the fractionalization of quantum spins into Majorana fermions, in addition to a phase transition associated with time reversal symmetry breaking. We show that the spin correlation develops around the crossover temperatures, whereas it shows a slight change at the critical temperature, as in other Kitaev-type models. We also calculate the excitation spectrum in terms of Majorana fermions, and find that the excitation gap in the non-Abelian phase is fragile against thermal fluctuations of the Z2fluxes, while that in the Abelian phase remains open.