From single particle to superfuid excitations in a dissipative polariton gas

TL;DR

This study investigates the transition from single particle to superfluid excitations in a dissipative polariton gas using advanced spectroscopic techniques, confirming Bogoliubov theory predictions in a non-equilibrium quantum fluid.

Contribution

It provides experimental evidence of Bogoliubov excitations in a dissipative polariton gas, highlighting the superfluid transition in a non-equilibrium setting.

Findings

Observation of positive and negative energy branches consistent with Bogoliubov theory

Identification of sound-wave-like excitation dispersion in a dense polariton gas

Analysis of non-equilibrium effects on the excitation spectrum

Abstract

Using angle-resolved heterodyne four-wave-mixing technique, we probe the low momentum excitation spectrum of a coherent polariton gas. The experimental results are well captured by the Bogoliubov transformation which describes the transition from single particle excitations of a normal fluid to sound-wave-like excitations of a superfluid. In a dense coherent polariton gas, we find all the characteristics of a Bogoliubov transformation, i.e. the positive and negative energy branch with respect to the polariton gas energy at rest, sound-wave-like shapes for the excitations dispersion, intensity and linewidth ratio between the two branches in agreement with the theory. The influence of the non-equilibrium character of the polariton gas is shown by a careful analysis of its dispersion.