# Chiral modes at exceptional points in exciton-polariton quantum fluids

## TL;DR

This paper demonstrates how to generate chiral vortex modes with fixed handedness in exciton-polariton quantum fluids by exploiting exceptional points in a non-Hermitian resonator, enabling control over orbital angular momentum states.

## Contribution

It introduces a method to produce chiral vortex modes at exceptional points in exciton-polariton systems, advancing control over topological states in quantum fluids.

## Key findings

- Vortex states with fixed orbital angular momentum are generated near exceptional points.
- Precise manipulation of the resonator's potential enables transition through the exceptional point.
- The approach can be extended to create high-order orbital angular momentum states.

## Abstract

We demonstrate generation of chiral modes -- vortex flows with fixed handedness in exciton-polariton quantum fluids. The chiral modes arise in the vicinity of exceptional points (non-Hermitian spectral degeneracies) in an optically-induced resonator for exciton polaritons. In particular, a vortex is generated by driving two dipole modes of the non-Hermitian ring resonator into degeneracy. Transition through the exceptional point in the space of the system's parameters is enabled by precise manipulation of real and imaginary parts of the closed-wall potential forming the resonator. As the system is driven to the vicinity of the exceptional point, we observe the formation of a vortex state with a fixed orbital angular momentum (topological charge). Our method can be extended to generate high-order orbital angular momentum states through coalescence of multiple non-Hermitian spectral degeneracies, which could find application in integrated optoelectronics.