Coherent electron-hole BCS state: Study of dynamics

The first experimental study of the evolution of a coherent electron-hole (e-h) BCS-like state in bulk GaAs at room temperature is presented. We explicitly demonstrate that the total spontaneous emission from e-h pairs located within the conduction and valence bands approaches zero when the radiative recombination of the e-h BCS state occurs. This confirms that a vast majority of electrons and holes available are condensed at the very bottoms of the bands and form the BCS state. The average lifetime of this state is measured to be around 300 fs. We also show that the coherence of electrons and holes of the BCS state is preserved for a much longer time compared to the intraband relaxation time T₂.