Dissipationless Spin Current Generation in Kitaev's Chiral Spin Liquid

TL;DR

This paper proposes that Kitaev's chiral spin liquid state in materials like $ ext{RuCl}_3$ can generate dissipationless spin currents via chiral Majorana edge modes, offering a new platform for spintronics.

Contribution

It introduces a universal scaling signature of chiral Majorana modes in the edge spin Seebeck effect and highlights the potential for highly integrated, efficient spin current devices using Kitaev materials.

Findings

Observation of half-quantized thermal Hall effect in $ ext{RuCl}_3$

Proposal of a universal scaling law for Majorana edge modes

Prediction of dissipationless spin current generation in Kitaev spin liquids

Abstract

$\alpha$-RuCl$_3$ is a promising candidate material for the Kitaev spin liquid state where the half quantization of the thermal Hall effect, suggesting a topological character, has been observed. However, its relation to the existence of chiral Majorana fermions, which is predicted from the theory of the Kitaev model, is still under debate. Here we propose a more direct signature of a chiral Majorana edge mode which emerges in a universal scaling of the Drude weight of the edge spin Seebeck effect in the Kitaev model. Moreover, the absence of backscatterings in the chiral edge mode results in the generation of a dissipationless spin current in spite of an extremely short spin correlation length close to a lattice constant in the bulk. This result is not only experimentally observable, but also opens a way towards spintronics application of Kitaev materials. In contrast to magnetically ordered systems, a Kitaev spin liquid state is stable even in the atomic scale and makes it possible to fabricate a highly integrated device with substantial efficiency to generate a spin current. This proposal for using $\alpha$-RuCl$_3$ as a nano-scale device will pioneer Kitaev spintronics.