Vestiges of Topological Phase Transitions in Kitaev Quantum Spin Liquids

• Published in: Physical review letters 2019-04, Vol.122 (14), p.147203-147203, Article 147203
• Main Authors: Go, Ara, Jung, Jun, Moon, Eun-Gook
• Format: Article
• Language: English
• Subjects: Fermions; Phase transitions; Ruthenium trichloride; Signatures; Spin liquid; Temperature; Topology
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.122.147203

We investigate signatures of topological quantum phase transitions (TQPTs) between the Z_{2} quantum spin liquids (QSLs). In two spatial dimensions, Z_{2} QSLs and their TQPTs are only well defined at zero temperature (T=0), and it is imperative to clarify their observable signatures under nonzero temperatures. Here, we present the vestiges of TQPTs between Z_{2} QSLs with Majorana fermions in terms of thermal Hall conductivity κ_{xy} at nonzero temperatures. The κ_{xy}/T shows characteristic temperature dependences around TQPTs. We argue that an exponential upturn near T=0 and the peak of κ_{xy}/T around massive excitation energy are observable smoking-gun signals of the TQPTs. Quantum critical fan-shape temperature dependences are uncovered across TQPTs. We also perform the parton mean-field analysis on a modified Kitaev model with next-nearest neighbor interactions finding TQPTs between the phases with different Chern numbers and their vestiges self-consistently. We discuss the implication of our results to the recent experiments in α-RuCl_{3}.