Charging energy and collective response of a quantum dot resonant tunneling device

Abstract

Recent self-consistent electronic structure calculations and linear response calculations of the current have sought to clarify the role of Coulomb charging of a flat quantum dot connected via tunneling barriers to a two-dimensional electron gas collector and emitter. In particular, resonant tunneling through such a structure, which is observed to be periodic in a gate voltage applied to the dot, is currently explained in terms of resonant suppression of the Coulomb blockade by the gate. Nonetheless questions remain regarding the off resonance activation energy and the possible role of collective excitations of the dot. We calculate the self-consistent electronic structure of a two-dimensional quantum dot connected via point-contact tunneling barriers to two wide 2DEG regions, in the Hartree approximation. We include the effect of finite source-drain voltage and side-gate voltages. We compute the charging energy for a single electron entering the dot and discuss the dot capacitance. Finally, we compute the approximate collective resonance frequency for charge oscillations in the dot and discuss the possibility of plasmon coupling to single-electron tunneling.