Magnetoelectric generation of a Majorana-Fermi surface in Kitaev's honeycomb model

TL;DR

This paper demonstrates that applying combined electric and magnetic fields to Kitaev's honeycomb model induces a Majorana-Fermi surface, leading to a stable gapless phase with metallic properties.

Contribution

The study derives an effective Hamiltonian showing how cross-perturbations create a Majorana-Fermi surface in Kitaev materials, a novel gapless phase.

Findings

Induction of a Majorana-Fermi surface via electric-magnetic field cross-term

Stable gapless phase with metallic thermodynamic behavior

Finite, non-quantized thermal Hall response

Abstract

We study the effects of static magnetic and electric fields on Kitaev's honeycomb model. Using the electric polarization operator appropriate for Kitaev materials, we derive the effective Hamiltonian for the emergent Majorana fermions to second-order in both the electric and magnetic fields. We find that while individually each perturbation does not qualitatively alter Kitaev spin liquid, the cross-term induces a finite chemical potential at each Dirac node, giving rise to a Majorana-Fermi surface. We argue this gapless phase is stable and exhibits typical metallic phenomenology, such as linear in temperature heat capacity and finite, but non-quantized, thermal Hall response. Finally, we speculate on the potential for realization of this physics in Kitaev materials.