Huge density-dependent blueshift of indirect excitons in biased coupled quantum wells

Abstract

We measure a dynamical blueshift of the indirect exciton in GaAs-coupled quantum wells of over 20 meV for carrier densities in the range 10 9 -10 12 cm Ϫ2 . We show that this shift is a many-body effect, which is proportional to the indirect exciton density over a broad range of densities, and it is accompanied by homogeneous broadening, which is proportional to the indirect exciton density.

Exciton-exciton interactions in quantum wells: Optical properties and energy and spin relaxation

“…As we already mentioned in the introduction, the density dependence of the exciton luminescence line shift, [1][2][3][4][5][6] the time dependence of line spin splitting and the luminescence depolarization [10][11][12][13]16,17] proved that all these phenomena come from exciton-exciton interaction. A theoretical study of these phenomena has been done by Fernández-Rossier et al [8,33], Ciuti et al [9], Amand et al [17], and Maialle et al [39].…”

“…The density dependent blue shift of the exciton line in GaAs/Al x Ga 1−x As symmetric coupled quantum wells, where electrons and holes are spatially separated by external gate voltage, has been recently measured by Butov et al [5] and Negoita et al [6]. Butov et al detected blue shift of 1.6 meV at zero magnetic field for wells width L = 80Å…”

“…Blue shift of the exciton luminescence line with growing exciton density was reported in single quantum wells [1,2], multiple quantum wells [3,4] and coupled quantum wells where electrons and holes are spatially separated [5,6]. The blue shift is attributed to the net exciton-exciton repulsion interaction in quantum wells [7][8][9].…”

“…Experimentally small exciton kinetic energy is achieved by resonant excitation at lattice temperature much lower than the binding energy [6,12,[15][16][17].…”

Spatially indirect excitons in coupled quantum wells

“…For spatially indirectXs in CQW, separation of the electron and hole in the z-direction gives rise to a dipole moment; therefore, the blue shift of X PL energy with X density is more pronounced due to dipole-diple interactions. This density dependent blue shift of indirect-X PL in GaAs/AlGaAs CQW systems has been reported [153,154] and was also detailed in Sec.…”