Discrete charging of a quantum dot strongly coupled to external leads

TL;DR

This paper investigates a quantum dot strongly coupled to external leads, revealing the existence of bound states with discrete charging behavior and Coulomb blockade effects, depending on the coupling strength and charging energy.

Contribution

It demonstrates analytically and numerically that strong coupling leads to bound states with discrete charging, a novel insight into quantum dot behavior.

Findings

At least N_dot - N bound states remain on the dot under strong coupling.

Bound states show discrete charging and Coulomb blockade effects.

Behavior varies with charging energy, showing repeated charging of superradiant states.

Abstract

We examine a quantum dot with $N_{\rm dot}$ levels which is strongly coupled to leads for varying number of channels $N$ in the leads. It is shown both analytically and numerically that for strong couplings between the dot and the leads, at least $N_{\rm dot}-N$ bound states (akin to subradiant states in optics) remain on the dot. These bound states exhibit discrete charging and, for a significant range of charging energies, strong Coulomb blockade behavior as function of the chemical potential. The physics changes for large charging energy where the same (superradiant) state is repeatedly charged.