Conditions and possible mechanism of condensation of e-h pairs in bulk GaAs at room temperature

TL;DR

This paper proposes a mechanism for the condensation of electron-hole pairs in bulk GaAs at room temperature, involving photon-assisted pairing at the band bottoms, resulting in a transient coherent bosonic state.

Contribution

It introduces a new explanation for e-h pair condensation in GaAs at room temperature based on high-density occupation and photon-assisted pairing.

Findings

Formation of a coherent e-h BCS-like state within hundreds of femtoseconds

High e-h density prevents pair destruction and coherency loss

Condensation occurs at the band bottoms due to photon-assisted pairing

Abstract

A mechanism of the condensation of e-h pairs in bulk GaAs at room temperature, which has been observed earlier, is proposed. The point is that the photon assisted pairing happens in a system of electrons and holes that occupy energy levels at the very bottoms of the bands. Due to a very high e-h density, the destruction of the pairs and loss of coherency does not occur because almost all energy levels inside a 30-60 meV band from the bottom of the conduction band prove to be occupied. As a result, a coherent ensemble of composite bosons (paired electrons and holes) with the minimum possible energy appears. The lifetime of this strongly non-equilibrium coherent e-h BCS-like state is as short as a few hundred of femtoseconds