Edge magnetization and spin transport in an SU(2)-symmetric Kitaev spin liquid

TL;DR

This paper explores edge magnetization and spin transport in an SU(2)-symmetric Kitaev spin liquid, revealing how magnetic fields and spin biases influence edge states and spin currents, providing potential probes for quantum spin liquids.

Contribution

It demonstrates the existence of nonlocal edge magnetization and characterizes spin transport properties in SU(2)-symmetric Kitaev spin liquids with Dirac and chiral excitations.

Findings

Zero-energy edge modes induce nonlocal magnetization.

Spin current exhibits power-law dependence on spin bias at zero temperature.

Edge magnetization and spin transport can probe charge-neutral edge states.

Abstract

We investigate the edge magnetism and the spin transport properties of an SU(2)-symmetric Kitaev spin liquid (KSL) model put forward by Yao and Lee [Phys. Rev. Lett. \textbf{107}, 087205 (2011)] on the honeycomb lattice. In this model, the spin degrees of freedom fractionalize into a $\mathbb{Z}_{2}$ static gauge field and three species of either gapless (Dirac) or gapped (chiral) Majorana fermionic excitations. We find that, when a magnetic field is applied to a zigzag edge, the Dirac KSL exhibits a nonlocal magnetization associated with the existence of zero-energy edge modes. The application of a spin bias $V=\mu_{\uparrow}-\mu_{\downarrow}$ at the interface of the spin system with a normal metal produces a spin current into the KSL, which depends, in the zero-temperature limit, as a power-law on $V$ for both Dirac and chiral KSLs, but with different exponents. Lastly, we study the longitudinal spin Seebeck effect, in which a spin current is driven by the combined action of a magnetic field perpendicular to the plane of the honeycomb lattice and a thermal gradient at the interface of the KSL with a metal. Our results suggest that edge magnetization and spin transport can be used to probe the existence of charge-neutral edge states in quantum spin liquids.