Tunneling spectroscopy of quantum spin liquids

TL;DR

This paper investigates tunneling spectroscopy signatures in quantum spin liquids, highlighting the spin gap as a key indicator of fractionalized excitations and proposing experimental setups to detect these features.

Contribution

It provides a theoretical analysis of tunneling conductance in Kitaev quantum spin liquids, including effects of magnetic fields and inelastic processes, applicable to various topological QSLs.

Findings

Spin-flip scattering causes a gaped conductance signature.

Magnetic field modifies spectral features in candidate materials.

Proposes lateral 1D tunnel junction as an experimental setup.

Abstract

We examine the spectroscopic signatures of tunneling through a Kitaev quantum spin liquid (QSL) barrier in a number of experimentally relevant geometries. We combine contributions from elastic and inelastic tunneling processes and find that spin-flip scattering at the itinerant spinon modes gives rise to a gaped contribution to the tunneling conductance spectrum. We address the spectral modifications that arise in a magnetic field necessary to drive the candidate material $\alpha$-RuCl$_3$ into a QSL phase, and we propose a lateral 1D tunnel junction as a viable setup in this regime. The characteristic spin gap is an unambiguous signature of the fractionalized QSL excitations, distinguishing it from magnons or phonons. The results of our analysis are generically applicable to a wide variety of topological QSL systems.