Suppression of level hybridization due to Coulomb interactions

TL;DR

This paper explores how Coulomb interactions can suppress level hybridization in a ring-stub system, affecting persistent currents and ensemble behavior, with implications for quantum coherence and electron interactions.

Contribution

It generalizes the concept of level hybridization to many-particle systems and analyzes the competition between hybridization and Coulomb interactions in a canonical ensemble.

Findings

Strong Coulomb interactions can isolate the ring from the stub, increasing persistent current.

Weak Coulomb interactions lead to behavior similar to grand canonical ensemble.

Sufficiently strong Coulomb interactions produce persistent currents characteristic of a canonical ensemble.

Abstract

We investigate an ensemble of systems formed by a ring enclosing a magnetic flux. The ring is coupled to a side stub via a tunneling junction and via Coulomb interaction. We generalize the notion of level hybridization due to the hopping, which is naturally defined only for one-particle problems, to the many-particle case, and we discuss the competition between the level hybridization and the Coulomb interaction. It is shown that strong enough Coulomb interactions can isolate the ring from the stub, thereby increasing the persistent current. Our model describes a strictly canonical system (the number of carriers is the same for all ensemble members). Nevertheless for small Coulomb interactions and a long side stub the model exhibits a persistent current typically associated with a grand canonical ensemble of rings and only if the Coulomb interactions are sufficiently strong does the model exhibit a persistent current which one expects from a canonical ensemble.