Coherent electron-hole BCS state: Study of dynamics

Smetanin

2006

Phys. Rev. B

It has been theoretically shown that in large-density semiconductor plasma there exist an energy level of a bound electron-hole pair (a composite boson) at the band gap. Filling this level up occurs through the condensation of electron-hole pairs with the use of mediating photons of a resonant electromagnetic field. We have demonstrated that in the case of a strong degeneracy of the plasma the critical temperature of the condensation is determined by the Fermi energies of the plasma components rather than the order parameter ∆. The critical temperature can exceed 300 K at electron-hole densities as large as 6 . 1018 cm -3 . The theoretical model is consistent with available experimental data.

Section: Mechanism Of Condensation Onto Bosonic Levelsmentioning

confidence: 99%

“…Superradiant emission in large-density nonequilibrium e-h systems in GaAs/AlGaAs p-i-n heterostructures was experimentally studied at room temperature [24][25][26][27][28] . The carrier density exceeded (2)(3)(4)(5)(6) .…”

mentioning

confidence: 99%

Condensation of electron-hole pairs in a degenerate semiconductor at room temperature

Smetanin

2006

Phys. Rev. B

“…We used similar structures as described elsewhere [8][9][10][11]. A characteristic feature of the structures is the presence of two sections along the axis of the device, one being an optical amplifier, while the other being an absorber.…”

Section: Methodsmentioning

confidence: 99%

“…The spectral maximum of the gain lies at the photon energy of 1.424 eV which corresponds 6 exactly to the lasing wavelength detected experimentally [8,9]. Just to remind, our structures have tree sections with independent pumping, two of which being amplifiers whereas the last one being an absorber (see [8][9][10][11] …”

Section: Optical Gain and Absorption In The Structurementioning

confidence: 99%

“…In particular, the polarization dephasing rate slows down with increasing density of the condensate. This implies that the destruction of coherency due to collisions does not happen despite of an enhanced collision rate with increasing density.In our recent experiments [8][9][10][11], we have studied the regime of the cooperative recombination in a highly non-equilibrium large density (> 3 . 10 18 cm -3 ) system of electrons and holes in bulk GaAs at room temperature.…”

mentioning

confidence: 99%

See 1 more Smart Citation

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

Physica Status Solidi (b)

2004

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. In the high-density limit, collectively paired electrons and holes behave like Cooper pairs in a superconductor, and the BCS-like energy gap at the Fermi level is the order parameter of the macroscopic quantum state [1,6]. As noted before [7], the order parameter of the excitonic condensate is identical to its optical polarization and can be directly accessed by relatively simple optical measurements. Moreover, it has been theoretically predicted that the dephasing and relaxation kinetics of excitonic condensate depends on its density in some cases [7]. In particular, the polarization dephasing rate slows down with increasing density of the condensate. This implies that the destruction of coherency due to collisions does not happen despite of an enhanced collision rate with increasing density.In our recent experiments [8][9][10][11], we have studied the regime of the cooperative recombination in a highly non-equilibrium large density (> 3 . 10 18 cm -3 ) system of electrons and holes in bulk GaAs at room temperature.The main information about the properties of the electron-

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

Physica Status Solidi (b)

2004