Landau levels of Majorana fermions in a spin liquid

TL;DR

This paper proposes a method to realize Landau levels for Majorana fermions in a strained Kitaev spin liquid, enabling the observation of Landau-level spectra through spin susceptibility measurements.

Contribution

It introduces a strained Kitaev model that creates Landau levels for Majorana fermions, a novel way to emulate magnetic field effects in a neutral quasiparticle system.

Findings

Landau levels observed in the Majorana spectrum due to strain-induced pseudo-magnetic fields.

Dynamic spin susceptibility reveals the Landau-level structure.

Strain engineering enables control over Majorana fermion excitations.

Abstract

Majorana fermions were originally proposed as elementary particles acting as their own antiparticles. In recent years, it has become clear that Majorana fermions can instead be realized in condensed-matter systems as emergent quasiparticles, a situation often accompanied by topological order. Here we propose a physical system which realizes Landau levels - highly degenerate single-particle states usually resulting from an orbital magnetic field acting on charged particles - for Majorana fermions. This is achieved in a variant of a quantum spin system due to Kitaev which is distorted by triaxial strain. This strained Kitaev model displays a spin-liquid phase with charge-neutral Majorana-fermion excitations whose spectrum corresponds to that of Landau levels, here arising from a tailored pseudo-magnetic field. We show that measuring the dynamic spin susceptibility reveals the Landau-level structure by a remarkable mechanism of probe-induced bound-state formation.