Semiconductor quantum kinetic equations with charge correlations and memory effects

Abstract

State Univeriity ofMoldova, Mateevici 60, 2009 Kishinau, MOLDOVA Email; klukanov@cinj!urm.md; N.A. Loiko, 1.Y Baburhkin, Institute of Physics, Academyof Sciences ofBelami, Scaryna Prorpekt 70,22W72 Minsk, BELARUS, Email: nloiko@dragon. bai.net. byCorrelation effects influencing the optical properties of semiconductors that cannot be described at the baais of Hartree-Fock approximation are intensively studied at the present time. Equations of motion methods,' the Green's function farmalism' or the cumulant expansion method with fluctuation-dissipation theorem' are successhdly used to explain distinctive features of optical spectra of semiconductors.In spite of the fact that all these different theories deal with just the same problem, the physical mechanisms and results obtained by using these theoretical methods are various in detail drasticauy Especially it concerm the coherently driven plasmons in high excited semiconductors. Our aim is to derive the equations of motion which contain the results of another theories and allow to include into considerations multi-quantum optical processes involving photon and se"-era1 mixed phonon-plasmons of frequencies w+, o . (m, and e are the eigen frequencies for longitudinal waves of the system).We get the semiconductor Bloch equations using the fluctuation-dissipation theorem to ~a ld a t e four operator expectation values with a~-* -6 -I -, -3 -2 -1 QThGl5 Fig. I. The spontaneous spectral function r versus the normalized photon frequency W = (ha-Eg)/hwg calculated using the total expression for r (a), taking into account only the first Sum in the expression (b) and the first and the second sums (c). N = 2 cm?, ho, = 31 mel? El = 2.7 el! KT = 1.5 mel? N = 5 IO'' cm-',m.=0.17m,,mh=0.7m,,E_=5.9,E,= 8.66.count of coherent memory effects. This method leads for the interband polarization Pk(t) to energy-conservation &functions with arguments of the form w -oB -,aknop. where w is the photon frequency, wp 1s the frequency of long-wavelength plasmonr, involving in process of optical interband transitions, and n is a number of plas-We investigate temperature and plasma concentration dependences of the spontaneous and stimulated radiation with account of multiquantum transitions. Thus, expression obtained for the spontaneous emission rate r(w) includes three different sums. They describe a contribution into the spontaneous radiation of different processes. Tne first sum accounts multi-quantum transitions in which photon and mixed phononplasmons of frequency ware involved. The second sum includes mixed phonon-plasmonr of frequenq w+ replicas. And at last, the third sum accounts emission of photon, mixed phononplasmons of frequency and a few short wavelengths LO phonons.Numerical calculations have been carried out for two sets of parameters typical for GaAs and ZnSe. These sets are different by B value of the Frahlich constant a, and lattice parameters Ep' me,* As a result, LO-phonon replicas in the spontaneous emission spectrum and carrier concentrations are more pronounced for ZnSe ...

Light-induced spatial gratings created by unipolar attosecond pulses coherently interacting with a resonant medium

“…The duration of femtosecond few-cycle pulses is much shorter than the relaxation time for the polarization T 2 and population inversion T 1 in most media, which allows coherent light-matter interaction to be achieved, [40][41][42][43] as well as the appearance of Rabi oscillations. In the papers [44,45], another phenomenon was predicted, which can arise during the coherent interaction of ultrashort bipolar pulses propagating through a resonant absorbing medium, namely, the creation, erasing and ultrafast control of polarization and population inversion gratings with a sequence of bipolar few-cycle pulses in the resonant medium.…”