Dynamics of visons and thermal Hall effect in perturbed Kitaev models

Abstract

A vison is an excitation of the Kitaev spin liquid which carries a Z2 gauge flux. While immobile in the pure Kitaev model, it becomes a dynamical degree of freedom in the presence of perturbations. We study an isolated vison in the isotropic Kitaev model perturbed by a small external magnetic field h, an offdiagonal exchange interactions Γ and a Heisenberg coupling J. In the ferromagnetic Kitaev model, the dressed vison obtains a dispersion linear in Γ and h and a fully universal low-T mobility, µ = 6v 2 m /T 2 , where vm is the velocity of Majorana fermions. In contrast, in the antiferromagnetic Kitaev model interference effects preclude coherent propagation and an incoherent Majorana-assisted hopping leads to a T -independent mobility. The motion of a single vison due to Heisenberg interactions is strongly suppressed for both signs of the Kitaev coupling. Vison bands induced by h are topological and lead to a characteristic peak in the thermal Hall effect as observed experimentally in α-RuCl3.

Berry Phases of Vison Transport in $\mathbb{Z}_2$ Topological Ordered States from Exact Fermion-Flux Lattice Dualities

“…Thus the Berry phase for e-particle movement can be calculated even for relatively large system sizes without too much computational cost. The lattice dualities developed in this work are universal and can be used to study not only the Berry phases of translations of visons but many other topological and dynamical properties of these excitations, such as their effective mass and dispersions, which can be crucial in understanding their role in real materials and experiments [37].…”