Capacitance in open quantum structures

Abstract

Opposite to the well-known statistical limit, we study a semiconductor quantum system with only one relevant resonance which is in contact with a probe acting as a particle reservoir. We find that the quasibound state that exists in the nearly closed system develops at a transition to the open system into a separate type of resonance. In contrast to the quasibound state (i) it is localized in the space between the probe and the isolated quantum system, (ii) its energy lies in the classically allowed regime, and (iii) its line shape is strongly asymmetric. Excellent quantitative agreement shows that this transition is seen in capacitance experiments on MIS (metal-insulator-semiconductor)-type semiconductor heterostructures in which a field-induced two-dimensional electron gas is formed.