Raman scattering in correlated thin films as a probe of chargeless surface states

TL;DR

This paper proposes using resonant light scattering to detect chargeless surface states in strongly interacting quantum spin systems, exemplified by the 3D hyperhoneycomb Kitaev model, enabling surface state characterization.

Contribution

It introduces resonant light scattering as a novel method to probe chargeless surface modes in strongly correlated systems, demonstrated through a detailed calculation for the Kitaev quantum spin liquid.

Findings

Resonant scattering couples efficiently to Majorana surface modes.

Surface contribution dominates the low-energy response in thin films.

Method enables identification of topological surface band structures.

Abstract

Several powerful techniques exist to detect topologically protected surface states of weakly-interacting electronic systems. In contrast, surface modes of strongly interacting systems which do not carry electric charge are much harder to detect. We propose resonant light scattering as a means of probing the chargeless surface modes of interacting quantum spin systems, and illustrate its efficacy by a concrete calculation for the 3D hyperhoneycomb Kitaev quantum spin liquid phase. We show that resonant scattering is required to efficiently couple to this model's sublattice polarized surface modes, comprised of emergent Majorana fermions that result from spin fractionalization. We demonstrate that the low-energy response is dominated by the surface contribution for thin films, allowing identification and characterization of emergent topological band structures.