Magnetic Field Symmetry And Phase Rigidity Of The Nonlinear Conductance In A Ring

We have performed nonlinear transport in a two-terminal ring showing the Aharonov-Bohni effect. We show experimentally that the nonlinear conductance is not symmetric in magnetic field, in contrast to the linear conductance. In addition, the asymmetry can be tuned by changing the potential of an electrostatic gate, showing that it is related to the phase accumulated by the electrons along the arms of the ring.