Many body shakeup in quantum well luminescence spectra

Abstract

The observation of many body shakeup in the photoluminescence spectra of InGaAs-InP quantum wells, in the quantum Hall regime, is reported. The occurrence of this many body effect is demonstrated from the observation of low energy satellites, corresponding to inter-Landau-level excitations of the degenerate electron gas. Comparison of the zero and finite magnetic field spectra shows that the low energy tail at 5=0 also arises from Fermi sea shakeup. The strength of the shakeup is controlled by the localization of the recombining hole, in agreement with recent theoretical predictions.PACS numbers: 73.20. Mf, 78.20.Ls, 78.55.Cr Many body processes can have a dramatic effect on the optical spectra of a degenerate electron gas (DEG) [1]. It has been known for more than twenty years that the spectra of x-ray transitions between the core states and the conduction band of a metal are strongly influenced by many body processes [2][3][4]. The most notable effects are the Fermi-energy edge singularity [2], and shakeup, the latter giving rise to the Anderson orthogonality catastrophe [3]. Recent advances in the growth of modulation-doped semiconductor heterostructures have made it feasible to investigate the similarities and differences between x-ray transitions of bulk three-dimensional metals and conduction-to-valence-band transitions of the quasitwo-dimensional (Q2D) DEG in semiconductors. In addition to the Fermi-energy edge singularity which was observed in 1987 [5], theory suggests that shakeup processes should occur in Q2D semiconductor systems [6-8]. We report an unequivocal experimental observation of shakeup in the photoluminescence (PL) of such a system. We also show that shakeup is strongly dependent on the localization of the valence-band hole, in agreement with theoretical predictions [7,8].Shakeup is a fundamental many body effect that occurs in optical transitions in the presence of a DEG, when the transition creates excitations of the DEG. These excitations are additional to the (electron or hole) quasiparticle that is added to the DEG in a one-electron picture of the transition. By energy conservation, the photon energy for shakeup processes in optical emission is lower than in the absence of shakeup, the difference corresponding to the energy of the excitations created. Pair excitations (composed of an electron and a hole quasiparticle on either side of the Fermi level) have a continuous range of energies, leading to a low-energy tail in the emission spectrum. In semiconductors there are many other sources of low-energy tails, with the result that the attribution of a low-energy tail to shakeup is usually based upon detailed analysis of the PL line shape. For example, low-energy tails in the recombination spectra of high density electron-hole plasmas in semiconductors have been attributed to many body plasmon emission processes, on the basis of a curve-fitting analysis of the PL line shape [9].

Trion states in a dense 2DEG

“…Hence, the PL spectrum will contain a fan of lines depending on magnetic field as In the case where M > N, the emission lines shift to low energies as: E T r −(M −N )hω c . These lines are called shake-up lines (SU ) [6]. As a rule the intensity of the SU lines is weak and it is difficult to observe more than two such lines in PL spectra.…”

Molecular States of Electrons: Emission of Single Molecules in Self-Organized InP/GaInP Quantum Dots

“…The SU emission occurs in many-electron systems when a recombining electron-hole pair excites surrounding electrons via the Coulomb interaction. In a 2DEG the SU emission appears at high magnetic fields via excitation of electrons into higher Landau www.intechopen.com levels and related magneto-plasmons (Butov et al, 1992;Hawrylak&Potemski, 1997;Nash et al, 1993). SU emission from the excited states was also observed in an InAs QD ensemble (Paskov et al, 2000).…”

Role of Hole Localization in the Magneto-Luminescence of a Two-Dimensional Electron Gas

“…Optical measurements on the high mobility two-dimensional electron system (2DES) have been performed over a long period [1][2][3][4][5][6][7][8][9][10][11][12][13] to study electron interactions through their effect on the optical emission properties. Many-body effects (329) have an influence on the optical spectra, as revealed by the appearance of charged excitons at low electron densities [11], shake-up processes [12], and optical singularities at the Fermi level (FES) [13].…”

“…Many-body effects (329) have an influence on the optical spectra, as revealed by the appearance of charged excitons at low electron densities [11], shake-up processes [12], and optical singularities at the Fermi level (FES) [13]. Most of the experimental work on optical emission by a 2DES has been done in the GaAs-AlGaAs system, due to the high electron mobility obtained at its interface.…”