Controllable high-speed polariton waves in a PT-symmetric lattice

TL;DR

This paper proposes a method to realize PT-symmetric lattices in exciton-polariton condensates, enabling high-speed, controllable polariton waves with potential applications in advanced photonic devices.

Contribution

It introduces a novel approach to fabricate PT-symmetric lattices in microcavities and demonstrates high-velocity polariton wave propagation controllable by external pulses.

Findings

High-velocity polariton waves can be achieved in nearly PT-symmetric lattices.

Wave velocity is controllable via an additional coherent pulse.

PT-symmetry breaks down when polariton lifetime exceeds a threshold.

Abstract

Parity-time (PT) symmetry gives rise to unusual phenomena in many physical systems, presently attracting a lot of attention. One essential and non-trivial task is the fabrication and design of the PT-symmetric lattices in different systems. Here we introduce a method to realize such a lattice in an exciton-polariton condensate in a planar semiconductor microcavity. We theoretically demonstrate that in the regime, where lattice profile is nearly PT-symmetric, a polariton wave can propagate at very high velocity resulting from the beating of a ground state condensate created in the lowest energy band at very small momentum and a condensate simultaneously created in higher energy states with large momentum. The spontaneous excitation of these two states in the nonlinear regime due to competition between multiple eigenmodes becomes possible since the spectrum of nearly PT-symmetric structure reveals practically identical amplification for Bloch waves from the entire Brillouin zone. There exists a wide velocity range for the resulting polariton wave. This velocity can be controlled by an additional coherent pulse carrying a specific momentum. We also discuss the breakup of the PT-symmetry when the polariton lifetime exceeds a certain threshold value.