Experimental evidence of condensation of electron-hole pairs at room temperature during femtosecond cooperative emission - art. no. 195209

Experimental results of the investigation of spectral characteristics of co operative emission of high-density e-h plasmas in bulk GaAs have been prese nted. It has been shown that the properties of electrons and holes during t he cooperative recombination are essentially different from these under las ing or normal spontaneous emission. The center of line of the cooperative e mission (1.405-1.406 eV) is shifted inside the band gap. It lies by about 1 9 meV and by nearly 40 meV lower than the peak wavelength of lasing and amp lified spontaneous emission, respectively. This corresponds to the e-h cond ensation at the bottoms of the bands. The features of the cooperative emiss ion can be explained in terms of e-h pairing and build-up of a transient co herent e-h BCS-like state. The estimated value of the order parameter Delta is around 2-3 meV.