Microscopic Model for a Strongly Correlated Superconducting Single-Electron-Transistor

TL;DR

This paper models a superconducting single-electron transistor with a ring of Hubbard clusters, showing how repulsive interactions can induce pairing and influence tunneling behaviors, revealing new mechanisms for superconductivity in nanoscale devices.

Contribution

It introduces a microscopic Hubbard-based model for a superconducting single-electron transistor driven by repulsive interactions, highlighting pairing mechanisms and tunneling regimes.

Findings

Weak effective interactions lead to pairing in Hubbard clusters.

System exhibits Coulomb blockade of two-electron tunneling.

Repulsion-induced pairs mimic phonon-induced pairing in tunneling patterns.

Abstract

We model a Superconducting Single-Electron Transistor operating by repulsive interactions. The device consists of a ring of Hubbard clusters, placed between electrodes and capacitively coupled to a gate potential. In each cluster, a pair of electrons at appropriate filling feels a weak effective interaction which leads to pairing in part of the parameter space. Thus, the system can host many bound pairs, with correlation induced binding. When the charging energy exceeds the pairing energy, single-electron tunneling prevails; in the opposite regime, we predict the Coulomb blockade pattern of two-electron tunneling. This suggests that in tunneling experiments repulsion-induced pairs may behave in a similar way as phonon-induced ones.