Coulomb correlations and coherent charge tunneling in mesoscopic coupled rings

TL;DR

This paper investigates how strong electron-electron interactions influence magnetic properties in coupled mesoscopic rings, revealing that correlations induce periodic magnetic responses and that charge fluctuations significantly affect oscillation periods.

Contribution

It demonstrates that strong correlations lead to periodic magnetic responses in coupled rings and shows how charge fluctuations and tunneling alter oscillation periods.

Findings

Strong e-e interactions induce periodic magnetic moments.

Charge fluctuations and tunneling modify oscillation periods.

Disorder effects are controllable via gate voltage.

Abstract

We study the effect of a strong electron-electron (e-e) interaction in a system of two concentric one-dimensional rings with incommensurate areas A_1 and A_2, coupled by a tunnel amplitude. For noninteracting particles the magnetic moment (persistent current) m of the many-body ground state and first excited states is an irregular function of the external magnetic field. In contrast, we show that when strong e-e interactions are present the magnetic field dependence of m becomes periodic. In such a strongly correlated system disorder can only be caused by inter-ring charge fluctuations, controllable by a gate voltage. The oscillation period of m is proportional to 1/(A_1 + A_2) if fluctuations are suppressed. Coherent inter-ring tunneling doubles the period when charge fluctuations are allowed.