Dynamics of vacancy-induced modes in the non-Abelian Kitaev spin liquid

TL;DR

This paper investigates how vacancies in a Kitaev spin liquid under a magnetic field create localized quasiparticle modes that influence dynamical spin correlations, with potential detection via STM.

Contribution

It introduces a model for vacancy-induced localized modes in the Kitaev spin liquid and explores their impact on dynamical responses and STM observability.

Findings

Localized vacancy modes produce a quasi-zero-frequency peak in spin correlations.

STM responses are sensitive to flux configurations, magnetic field, and vacancy levels.

The model explains the hybridization of localized modes and their spectral signatures.

Abstract

We study the dynamical response of vacancy-induced quasiparticle excitations in the site-diluted Kitaev spin liquid with a magnetic field. Due to the flux-binding effect and the emergence of dangling Majorana fermions around each spin vacancy, the low-energy physics is governed by a set of vacancy-induced quasi-zero-energy modes. These localized modes result in unique characteristics of the dynamical spin correlation functions, which intriguingly mimic the single-quasiparticle density of states and further exhibit a quasi-zero-frequency peak. By recognizing the potential observability of these local correlation functions via scanning tunneling microscopy (STM), we show how the STM response is sensitive to the local flux configuration, the magnetic field strength, and the vacancy concentration. Constructing a simple model of the localized modes, we also elucidate how the local correlation functions can be interpreted in terms of the hybridization between these modes.