Gapless excitations in non-Abelian Kitaev spin liquids with line defects

TL;DR

This paper demonstrates that line defects in non-Abelian Kitaev spin liquids can host gapless Majorana modes under certain conditions, with implications for understanding experimental observations in $ ext{RuCl}_3$.

Contribution

It identifies conditions for gapless Majorana modes at line defects and calculates related relaxation rates, connecting theory with experiments.

Findings

Line defects host gapless Majorana modes below a critical interaction.

Critical interaction depends on external magnetic field.

Calculated relaxation rate matches experimental data in $ ext{RuCl}_3$.

Abstract

We show that line defects in a non-Abelian Kitaev spin liquid harbor gapless one-dimensional Majorana modes if the interaction across the defect falls below a critical value. Treating the weak interaction at the line defect within a mean-field approximation, we determine the critical interaction strength as a function of the external magnetic field. In the gapless regime, we use the low-energy effective field theory to calculate the spin-lattice relaxation rate for a nuclear spin near the defect and find a cubic temperature dependence that agrees with experiments in the Kitaev material $\alpha\text{-RuCl}_3$.