Quantum spin liquids (QSLs) are intriguing phases of matter possessing fractionalized excitations. Several quasi-two dimensional materials have been proposed as candidate QSLs, but direct evidence for fractionalization in these systems is still lacking. In this paper, we show that the inter-plane thermal conductivity in layered QSLs carries a unique signature of fractionalization. We examine several types of gapless QSL phases - a Z2 QSL with either a Dirac spectrum or a spinon Fermi surface, and a U(1) QSL with a Fermi surface. In all cases, the in-plane and c−axis thermal conductivities have a different power law dependence on temperature, due to the different mechanisms of transport in the two directions: in the planes, the thermal current is carried by fractionalized excitations, whereas the inter-plane current is carried by integer (non-fractional) excitations. In layered Z2 and U(1) QSLs with a Fermi surface, the c−axis thermal conductivity is parametrically smaller than the in-plane one, but parametrically larger than the phonon contribution at low temperatures.
@article{arxiv.1708.02584,
title = {Signatures of fractionalization in spin liquids from interlayer thermal transport},
author = {Yochai Werman and Shubhayu Chatterjee and Siddhardh C. Morampudi and Erez Berg},
journal= {arXiv preprint arXiv:1708.02584},
year = {2018}
}