Fast pulsed photoemission from a double quantum well on a dielectric substrate as a dynamic process of inverse LEED leading to the generation of a charge and current density wave

Within the framework of the rigorous quantum theory of the atomic photoeffect and the scenario of photoemission from a crystal as an inverse LEED process, pulsed photoemission from a flat thin-film photoemitter formed by a double quantum well on a dielectric substrate is investigated. The spatio-temporal dependences of the charge and current densities are calculated using the density matrix method. Asymptotic estimates are made in terms of the evolution of wave packets and the concepts of the extreme phase and fastest descent. The possibility of generating charge and current density waves as a result of the population and decay of quasi-stationary states of a doublet of a double quantum well under photoexcitation of electrons in conducting layers from inside this well is shown. For comparison, calculations were made for photoemission from a metal film on a substrate without a heterostructure: the double-well heterostructure increases, stabilizes, and extends the photocurrent pulse. A comparison of the contributions of the outgoing and incoming waves of the inverse LEED problem is made, and the relative smallness of the contribution of the incoming wave is quantitatively demonstrated.