Diamagnetic persistent currents and spontaneous time-reversal symmetry breaking in mesoscopic structures

Recently, new strongly interacting phases have been uncovered in mesoscopic systems with chaotic scattering at the boundaries. The new phases are the mesoscopic analogue of spontaneous distortions of the Fermi surface induced by interactions in bulk systems and can occur in any Fermi-liquid channel with angular momentum m. Here we show that the phase with m even has a diamagnetic persistent current (seen experimentally but mysterious theoretically), while that with m odd can be driven through a transition which spontaneously breaks time-reversal symmetry by increasing the coupling to dissipative leads. Our analysis is reliable when the dimensionless conductance of the system is large, is nonperturbative in both disorder and interactions, and applies to ballistic structures with strong interactions.