Realization of Hofstadter's butterfly and a one-way edge mode in a polaritonic system

TL;DR

This paper demonstrates how to create an artificial magnetic field in a polaritonic lattice, leading to Hofstadter's butterfly, chiral edge states, and potential topological lasing, advancing topological photonics in neutral bosonic systems.

Contribution

It introduces a static scheme to generate artificial gauge fields in polariton systems, enabling observation of Hofstadter's butterfly and topological lasing without periodic modulation.

Findings

Observation of Hofstadter's butterfly pattern.

Detection of chiral edge states in the lattice.

Proposal for robust topological lasing in polariton systems.

Abstract

We present a scheme to generate an artificial gauge field for the system of neutral bosons, represented by polaritons in micropillars arranged into a square lattice. The splitting between the two polarizations of the micropillars breaks the time-reversal symmetry (TRS) and results in the effective phase-dependent hopping between cavities. This can allow for engineering a nonzero flux on the plaquette, corresponding to an artificial magnetic field. Changing the phase, we observe a characteristic Hofstadter's butterfly pattern and the appearance of chiral edge states for a finite-size structure. For long-lived polaritons, we show that the propagation of wave packets at the edge is robust against disorder. Moreover, given the inherent driven-dissipative nature of polariton lattices, we find that the system can exhibit topological lasing, recently discovered for active ring cavity arrays. The results point to a static way to realize artificial magnetic field in neutral spinful systems, avoiding the periodic modulation of the parameters or strong spin-orbit interaction. Ultimately, the described system can allow for high-power topological single-mode lasing which is robust to imperfections.