Anisotropic exciton polariton pairs as a platform for PT-symmetric non-Hermitian physics

TL;DR

This paper proposes using anisotropic exciton-polariton pairs in microcavities as a novel quantum platform to realize PT-symmetry and Exceptional Points, enabling advanced non-Hermitian physics and potential zero-threshold lasers.

Contribution

It introduces a new quantum system based on anisotropic exciton-polaritons for PT-symmetry and Exceptional Points, expanding non-Hermitian physics beyond classical optical systems.

Findings

Observation of polarization-tunable Exceptional Points

Identification of Voigt EPs with birefringence compensation

Potential for zero-threshold laser development

Abstract

Non-Hermitian systems with parity-time (PT) symmetry have been realized using optical constructs in the classical domain, leading to a plethora of non-intuitive phenomena. However, PT-symmetry in purely quantum non-Hermitian systems like microcavity exciton-polaritons has not been realized so far. Here we show how a pair of nearly orthogonal sets of anisotropic exciton-polaritons can offer a versatile platform for realizing multiple spectral degeneracies called Exceptional Points (EPs) and propose a roadmap to achieve a PT-symmetric system. Polarization-tunable coupling strength creates one class of EPs, while Voigt EPs are observed for specific orientations where splitting of polariton modes due to birefringence is compensated by Transverse Electric (TE) -Transverse Magnetic (TM) mode splitting. Thus, paired sets of polarized anisotropic microcavity exciton-polaritons can offer a promising platform not only for fundamental research in non-Hermitian quantum physics and topological polaritons, but also, we propose that it will be critical for realizing zero threshold lasers.