Thermal transport in a two-dimensional $\mathbb{Z}_2$ spin liquid

TL;DR

This paper investigates the thermal conductivity of the two-dimensional Kitaev spin model, revealing how fractionalization and gauge fields influence heat transport, with implications for understanding quantum spin liquids.

Contribution

It provides a comprehensive analysis combining exact diagonalization and mean-field approaches to understand thermal transport in a $ ext{Z}_2$ spin liquid, highlighting the role of gauge fluctuations.

Findings

Temperature-dependent spectral intensity due to fractionalization

Emergence of a pseudogap from gauge field disorder

Dissipative heat conduction behavior

Abstract

We study the dynamical thermal conductivity of the two-dimensional Kitaev spin-model on the honeycomb lattice. We find a strongly temperature dependent low-frequency spectral intensity as a direct consequence of fractionalization of spins into mobile Majorana matter and a static $\mathbb{Z}_{2}$ gauge field. The latter acts as an emergent thermally activated disorder, leading to the appearance of a pseudogap which partially closes in the thermodynamic limit, indicating a dissipative heat conductor. Our analysis is based on complementary calculations of the current correlation function, comprising exact diagonalization by means of a complete summation over all gauge sectors, as well as a phenomenological mean-field treatment of thermal gauge fluctuations, valid at intermediate and high temperatures. The results will also be contrasted against the conductivity discarding gauge fluctuations.