We calculate electron transmission through a point barrier oscillating at frequency ω. Transmission resonances occur before the first emitted sideband channel opens, that is, for electron energies E≤ħω, and which strongly suggest the formation of quasibound states in the time-dependent potential. We confirm the existence of these quasibound states, obtaining both the binding energy and electron lifetime, by computing the complex energy poles of the transmission amplitude. The resulting transmission resonances are analogous to those found in other multiple quantum channel scattering problems, such as the transmission through a donor impurity in a quasi-one-dimensional wire.

• Received 21 August 1992

DOI:https://doi.org/10.1103/PhysRevB.46.15329