Bound states in the continuum driven by AC fields

Abstract

We report on the formation of bound states in the continuum driven by AC fields. The considered system consists of a quantum ring connected to two leads. An AC side-gate voltage controls the interference of electrons passing through the system. We model the system by two sites in parallel connected to two semi-infinite lattices. The energy of these sites changes harmonically with time. We obtain the transmission probability and the local density of states at the ring sites and show that transmission probability displays a Fano profile when the energy of the incoming electron approaches the driving frequency. Correspondingly, the local density of states presents a narrow peak that approaches a delta-function in the weak-coupling limit. We attribute these features to the presence of bound states in the continuum.