Dynamical Fano resonance of an exciton in laser-driven semiconductor superlattices

An excitonic Floquet state in semiconductor superlattices (SLs) driven by an intense monochromatic laser is examined based on multichannel scattering theory, where this state is supported by a photon sideband attributed to a SL joint miniband. It is shown that the excitonic Fano resonance (FR) is caused by the coupling between photon sidebands, and thus one obtains the possibility of dynamic quantum control of this exciton state by means of laser tuning. This FR differs from the conventional FR observed in the original SLs without laser irradiation in that the latter FR results from the static Coulomb coupling between different SL joint minibands. Both the q parameter and the spectral width Γ associated with the excitonic FR of concern vary notably with a change of laser strength. In particular, it is found that the FR is made stable, that is, 1/qand Γ become minimized, when the laser strength is appropriately tuned to the condition of what is called dynamic localization