Coherent nonlinear transport in quantum rings

While equilibrium properties of mesoscopic systems are well understood, many questions are still debated concerning the non-equilibrium properties, which govern nonlinear transport. Nonlinear transport measurements have been performed on two-terminal semiconductor quantum rings in the open regime, where the rings are used as electron interferometers and show the Aharonov–Bohm effect. We observe a magnetic field asymmetry of the nonlinear conductance, compatible with the non-validity of the Onsager–Casimir relations out-of-equilibrium. In particular, the voltage-antisymmetric part of the nonlinear conductance of these two-terminal devices is not phase rigid, as it is the case for the linear conductance. We show that this asymmetry is directly related to the electronic phase accumulated by the electrons along the arms of the ring and can be tuned using an electrostatic gate.