Divergence of Majorana-Phonon Scattering in Kitaev Quantum Spin Liquid

TL;DR

This paper investigates the divergence in Majorana-phonon scattering in the Kitaev quantum spin liquid, revealing velocity-dependent interactions that could explain anomalous thermal properties in RuCl$_3$ and aid in detecting fractionalized quasiparticles.

Contribution

It analytically derives the velocity-dependent Majorana-phonon scattering and identifies conditions for divergence, linking theoretical predictions with experimental data in RuCl$_3$.

Findings

Divergence occurs when Majorana fermions and phonons share the same velocity.

Experimental phonon velocity in RuCl$_3$ constrains the Kitaev interaction range.

Highlights the importance of lattice excitations in understanding quantum spin liquids.

Abstract

Magnetoelastic interaction couples spin and lattice degrees of freedom and plays a key role in thermal transport properties of magnetic insulators. In the Kitaev quantum spin liquid, the low energy excitations are charge neutral Majorana fermions, which transform the magnetoelasctic interaction into Majorana-phonon scattering. Motivated by anomalous thermal properties of the Kitaev quantum spin liquid candidate RuCl$_3$, in this letter, we combine meV resolution inelastic x-ray scattering and theoretical calculation to examine the Majorana-phonon scattering. We analytically derive the velocity-dependent Majorana-phonon scattering and find a divergence when the acoustic phonons and the itinerant Majorana fermions have the same velocity. Based on the experimentally determined acoustic phonon velocity in RuCl$_3$, we estimate the range in the Kitaev interaction for which divergent Majorana-phonon scattering can happen. Our result opens a new avenue to uncover fractionalized quasiparticles in the Kitaev quantum spin liquid and emphasizes the critical role of lattice excitations in RuCl$_3$.