Local Probes for Charge-Neutral Edge States in Two-Dimensional Quantum Magnets

TL;DR

This paper proposes using spin-polarized scanning tunneling microscopy to directly detect charge-neutral topological edge states in quantum magnets, demonstrated through the Kitaev honeycomb model and kagome magnon insulator.

Contribution

It introduces a novel local probing method for topological edge states in charge-neutral quantum magnetic systems, leveraging existing technology.

Findings

Signatures of topological edge states can be extracted from local structure factor measurements.

Contrasting bulk and edge conductance reveals fractionalized excitations.

Method is applicable to various quantum magnetic topological phases.

Abstract

The bulk-boundary correspondence is a defining feature of topological states of matter. However, for quantum magnets such as spin liquids or topological magnon insulators a direct observation of topological surface states has proven challenging because of the charge-neutral character of the excitations. Here we propose spin-polarized scanning tunneling microscopy as a spin-sensitive local probe to provide direct information about charge neutral topological edge states. We show how their signatures, imprinted in the local structure factor, can be extracted by specifically employing the strengths of existing technologies. As our main example, we determine the dynamical spin correlations of the Kitaev honeycomb model with open boundaries. We show that by contrasting conductance measurements of bulk and edge locations, one can extract direct signatures of the existence of fractionalized excitations and non-trivial topology. The broad applicability of this approach is corroborated by a second example of a kagome topological magnon insulator.