COULOMB CORRELATIONS AND COHERENT CHARGE TUNNELING IN MESOSCOPIC COUPLED RINGS

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 in teractions are present the magnetic-field dependence of m becomes peri odic. In such a strongly correlated system disorder can only be caused by inter-ring charge fluctuations, controllable by a gate voltage. Th e oscillation period of m is proportional to 1/(A(1) + A(2)) if fluctu ations are suppressed. Coherent inter-ring tunneling doubles the perio d when charge fluctuations are allowed.