Broken symmetry and competing orders in Weyl semimetal interfaces

TL;DR

This paper explores how interactions in Weyl semimetal interfaces lead to various broken symmetry states, including exciton condensates, charge density waves, and supersolid phases, with potential experimental signatures.

Contribution

It introduces the concept of competing and coexisting broken symmetries in Weyl semimetal surfaces, highlighting the formation of exciton condensates and supersolid states due to Coulomb interactions.

Findings

Formation of interlayer exciton condensates with specific flavor dependencies

Identification of a particle-hole FFLO-like state for well-nested Fermi arcs

Induction of charge density wave order leading to a supersolid phase

Abstract

We consider interaction-induced broken symmetry states of two Weyl semimetal surfaces with multiple Fermi-arc (FA) states. In the presence of inter- and intra-surface Coulomb interactions, multiple broken symmetries may emerge which coexist and/or compete with one another. Interlayer exciton condensates involving different FA flavors are shown to form, with amplitudes determined by the strength of interactions and the degree of nesting among the arcs. For FA pairs which are well-separated in momentum with strong nesting, the resulting state is a particle-hole analog of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconductor. Intralayer interactions moreover induce charge density wave (CDW) ordering, so that the most general state of the system is a supersolid. These orderings in principle carry signatures in non-linear behavior and narrow band noise in Coulomb drag transport measurements.