Dynamic resonant tunneling via a quasibound superstate

Abstract

The quantum tunneling current via an opaque barrier with an oscillating well reveals a wealth of physical phenomena: eigenstate-assisted activation, the elevator effect, coherent destruction of tunneling, suppression of activation, and the Sisyphus effect are a few examples. In this paper, we investigate these effects from a different perspective---transmission via a quasibound super state (QBSS). It is shown that an oscillating well supports a QBSS, which consists of numerous quasibound substates. Each one of these substates has a finite spectral width, which corresponds to the escape probability. However, they construct a unique spectrum, which consists of activated and suppressed quasi substates all of which are simultaneously excited. Thus, when the oscillating well is integrated into an opaque barrier, one can borrow an analogy from stationary resonant tunneling (RT). In the stationary RT scenario, current flows via a quasibound state. In the oscillating RT scenario, current flows via a QBSS. This analogy can easily explain many of the system's complex behaviors: the symmetry between the current's sensitivity to the incoming energy and the outgoing one, and even why some frequencies induce activation while others suppress it. This analogy can be applied to improve the sensitivity of the system when used for a frequency-controlled transistor for it predicts that when the incoming energy is shifted from the central resonance of the QBSS, the device's current becomes exponentially sensitive to the applied frequency. While the oscillations' frequency mainly determines the spectral distance between substates, the oscillations' amplitude determines the spectral width and center of the QBSS. Furthermore, it is suggested that this analogy can be applied to investigate microbiological systems (the olfactory system) and optical devices.