Polaritonic Chern insulators in monolayer semiconductors

TL;DR

This paper demonstrates the creation of polaritonic Chern insulators in monolayer semiconductors by coupling valley excitons with photonic modes, revealing topological phases with potential for advanced polaritonic devices.

Contribution

It introduces a novel method to realize polaritonic Chern insulators using TMDs and photonic crystals, highlighting the role of symmetry breaking in topological phase transitions.

Findings

Identification of polaritonic Dirac points as topological markers

Prediction of chiral edge states within topological gaps

Numerical evidence of non-zero Chern numbers in polaritonic bands

Abstract

Systems with strong light-matter interaction opens up new avenues for studying topological phases of matter. Examples include exciton-polaritons, mixed light-matter quasiparticles, where the topology of the polaritonic band structure arises from the collective coupling between matter wave and optical fields strongly confined in periodic dielectric structures. Distinct from light-matter interaction in a uniform environment, the spatially varying nature of the optical fields leads to a fundamental modification of the well-known optical selection rules, which were derived under the plane wave approximation. Here we identify polaritonic Chern insulators by coupling valley excitons in transition metal dichalcogenides (TMDs) to photonic Bloch modes in a dielectric photonic crystal (PhC) slab. We show that polaritonic Dirac points (DPs), which are markers for topological phase transition points, can be constructed from the collective coupling between valley excitons and photonic Dirac cones in the presence of both time-reversal and inversion symmetries. Lifting exciton valley degeneracy by breaking time-reversal symmetry leads to gapped polaritonic bands with non-zero Chern numbers. Through numerical simulations, we predict polaritonic chiral edge states residing inside the topological gaps. Our work paves the way to further explore polaritonic topological phases and their practical applications in polaritonic devices.