Linear and Nonlinear Optical Responses in Kitaev Spin Liquids

TL;DR

This paper explores how intense THz laser pulses induce high-harmonic generation in Kitaev spin liquids, revealing unique spectra linked to Majorana fermions and magnetic field effects, offering a new way to probe quantum spin liquids.

Contribution

It introduces a theoretical framework for HHG in Kitaev spin liquids, highlighting the role of dynamical symmetry breaking and Majorana excitations in the spectra, which was not previously understood.

Findings

HHG spectra show characteristic continua of Majorana fermions.

Static electric/magnetic fields can control the HHG spectral peaks.

Magnetic field dependence of HHG differs from ordered magnets.

Abstract

We theoretically study THz-light-driven high-harmonic generation (HHG) in the spin-liquid states of the Kitaev honeycomb model with a magnetostriction coupling between spin and electric polarization. To compute the HHG spectra, we numerically solve the Lindblad equation, taking account of the dissipation effect. We find that isotropic Kitaev models possess a dynamical symmetry, which is broken by a static electric field, analogous to HHG in electron systems. We show that the HHG spectra exhibit characteristic continua of Majorana fermion excitations, and their broad peaks can be controlled by applying static electric or magnetic fields. In particular, the magnetic-field dependence of the HHG spectra drastically differs from those of usual ordered magnets. These results indicate that an intense THz laser provides a powerful tool to observe dynamic features of quantum spin liquids.