Doublet structures in quantum well absorption spectra due to Fano-related interference

摘要

In this theoretical investigation we predict an unusual interaction between adiscrete state and a continuum of states, which is closely related to the caseof Fano-interference. It occurs in a GaAs/AlxGa1-xAs quantum well between thelowest light-hole exciton and the continuum of the second heavy-hole exciton.Unlike the typical case for Fano-resonance, the discrete state here is outsidethe continuum; we use uniaxial stress to tune its position with respect to theonset of the continuum. State-of-the art calculations of absorption spectrashow that as the discrete state approaches the continuum, a doublet structureforms which reveals anticrossing behaviour. The minimum separation energy ofthe anticrossing depends characteristically on the well width and is unusuallylarge for narrow wells. This offers striking evidence for the strong underlyingvalence-band mixing. Moreover, it proves that previous explanations of similardoublets in experimental data, employing simple two-state models, areincomplete.