Quantum pump driven fermionic Mach-Zehnder interferometer

Abstract

We have investigated the characteristics of the currents in a pump driven fermionic Mach-Zehnder interferometer. The system is implemented in a conductor in the quantum Hall regime, with the two interferometer arms enclosing an Aharonov-Bohm flux Phi. Two quantum point contacts with transparency modulated periodically in time drive the current and act as beam splitters. The current has a flux-dependent part I-(Phi) as well as a flux-independent part I-(0). Both current parts show oscillations as a function of frequency on the two scales determined by the lengths of the interferometer arms. In the nonadiabatic, high-frequency regime I-(Phi) oscillates with a constant amplitude while the amplitude of the oscillations of I-(0) increases linearly with frequency. The flux-independent part I-(0) is insensitive to temperature while the flux-dependent part I-(Phi) is exponentially suppressed with increasing temperature. We also find that for low amplitude, adiabatic pumping rectification effects are absent for semitransparent beam splitters. Inelastic dephasing is introduced by coupling one of the interferometer arms to a voltage probe. For a long charge relaxation time of the voltage probe, giving a constant probe potential, I-(Phi) and the part of I-(0) flowing in the arm connected to the probe are suppressed with increased coupling to the probe. For a short relaxation time, with the potential of the probe adjusting instantaneously to give zero time-dependent current at the probe, only I-(Phi) is suppressed by the coupling to the probe.