Exciton center-of-mass dispersion in semiconductor quantum wells

Abstract

We discuss the results of the calculation of the exciton center-of-mass dispersion in a semiconductor quantum well. Strong nonparabolicity arises due to the coupling among the excitons related to the heavy and light holes. We consider the effects of the coupling in the exciton dynamics by calculating the exciton average mass and spin.

Center-of-mass properties of the exciton in quantum wells

“…This is one of the reasons why the expansion Eqs. (13,14) gives very good results with just two subbands, while an expansions in the subband states at the Γ-point [18] needs more subbands for the same accuracy.…”

“…[17] β = 1 (in the parabolic case m e = ∞) was taken in order for the form factors (17) to be independent of Q, and in Ref. [18] no particular choice or handling of β is mentioned. In analytic expressions, usually the symmetric (in the parabolic case m e = m h ) value β = 1/2 is taken [16].…”

“…The HH 1 C 1 − 2p + exciton has at Q = 0 a slightly lower energy than the HH 1 C 1 − 2p − (third state at Q = 0) because it couples to the LH 1 C 1 − 1s outside of the Γ-point. [18] (gray) for the 5 nm QW (shifted to match at Q = 0). The exact HH1-subband dispersion for the parameters of [18] is plotted, too (diamonds).…”

“…[18] (gray) for the 5 nm QW (shifted to match at Q = 0). The exact HH1-subband dispersion for the parameters of [18] is plotted, too (diamonds).…”

“…The numerical effort for such calculations remains reasonable due to the high symmetry of this point. In contrast, only a few publications on multiband calculations of exciton COM dispersions in QW exist ( [17][18][19]) since these are very demanding. Methods for improving the numerical accuracy and reducing the effort of such calculations are clearly necessary.…”