Quantized thermal Hall conductance from edge current calculations in lattice models

Abstract

The quantized thermal Hall effect is an important probe for detecting chiral topological order and revealing the nature of chiral gapless edge states. The standard Kubo formula approach for the thermal Hall conductance $\kappa_{xy}$ based on the linear-response theory faces difficulties in practical application due to the lack of a reliable numerical method for calculating dynamical quantities in microscopic models at finite temperature. In this work, we propose an approach for calculating $\kappa_{xy}$ in two-dimensional lattice models displaying chiral topological order. Our approach targets at the edge current localized at the boundary which involves only thermal averages of local operators in equilibrium, thus drastically lowering the barrier for the calculation of $\kappa_{xy}$. We use the chiral $p$-wave superconductor (with and without disorder) and the Hofstadter model as benchmark examples to illustrate several sources of finite-size effects, and we suggest the infinite (or sufficiently long) strip as the best geometry for carrying out numerical simulations.