Magnetoasymmetric transport in a mesoscopic interferometer: From the weak to the strong coupling regime

Abstract

The microreversibility principle implies that the conductance of a two-terminal Aharonov-Bohm interferometer is an even function of the applied magnetic flux. Away from linear response, however, this symmetry is not fulfilled and the conductance phase of the interferometer when a quantum dot is inserted in one of its arms can be a continuous function of the bias voltage. Such magnetoasymmetries have been investigated in related mesoscopic systems and arise as a consequence of the asymetric response of the internal potential of the conductor out of equilibrium. Here we discuss magnetoasymmetries in quantum-dot Aharonov-Bohm interferometers when strong electron-electron interactions are taken into account beyond the mean-field approach. We find that at very low temperatures the asymmetric element of the differential conductance shows an abrupt change for voltages around the Fermi level. At higher temperatures we recover a smooth variation of the magnetoasymmetry as a function of the bias. We illustrate our results with the aid of the electron occupation at the dot, demonstrating that its nonequilibrium component is an asymmetric function of the flux even to lowest order in voltage. We also calculate the magnetoasymmetry of the current-current correlations (the noise) and find that it is given, to a good extent, by the magnetoasymmetry of the weakly nonlinear conductance term. Therefore, both magnetoasymmetries (noise and conductance) are related to each other via a higher-order fluctuation-dissipation relation. This result appears to be true even in the low-temperature regime, where Kondo physics and many-body effects dominate the transport properties.