Chiral phase transition and thermal Hall effect in an anisotropic spin model on the kagome lattice

Abstract

We present a study of the thermal Hall effect in the extended Heisenberg model with XXZ anisotropy in the kagome lattice. This model has the particularity that, in the classical case, and for a broad region in parameter space, an external magnetic field induces a chiral symmetry breaking: the ground state is a doubly degenerate q = 0 order with either positive or negative net chirality. Here, we focus on the effect of this chiral phase transition in the thermal Hall conductivity using Linear-Spin-Waves theory. We explore the topology and calculate the Chern numbers of the magnonic bands, obtaining a variety of topological phase transitions. We also compute the quantum corrections to the critical temperature associated with the chiral phase transition (T SW c ). Our main result is that, the thermal Hall conductivity, which is nul for T > T SW c , becomes non-zero as a consequence of the spontaneaous chiral symmetry breaking at low temperatures. Therefore, we present a simple model where it is possible to "switch" on/off the thermal transport properties introducing a magnetic field and heating or cooling the system.