Decay and coherence of two-photon excited yellow ortho-excitons in Cu2O

TL;DR

This paper investigates the decay and coherence properties of two-photon excited ortho-excitons in Cu2O, revealing insights into exciton dynamics, quantum saturation effects, and polaritonic oscillations using spectroscopic methods.

Contribution

It introduces a novel two-photon excitation technique for high-density excitonic gases and provides a semiclassical analysis of polaritonic oscillations affecting exciton coherence.

Findings

Quantum saturation limits Bose-Einstein condensation of ortho-excitons.

Oscillations in luminescence decay are explained by polaritonic beating.

Cooling and recombination rates influence exciton gas behavior.

Abstract

Photoluminescence excitation spectroscopy has revealed a novel, highly efficient two-photon excitation method to produce a cold, uniformly distributed high density excitonic gas in bulk cuprous oxide. A study of the time evolution of the density, temperature and chemical potential of the exciton gas shows that the so called quantum saturation effect that prevents Bose-Einstein condensation of the ortho-exciton gas originates from an unfavorable ratio between the cooling and recombination rates. Oscillations observed in the temporal decay of the ortho-excitonic luminescence intensity are discussed in terms of polaritonic beating. We present the semiclassical description of polaritonic oscillations in linear and non-linear optical processes.