Quantum pump driven fermionic Mach-Zehnder interferometer

TL;DR

This paper investigates the behavior of currents in a quantum Hall fermionic Mach-Zehnder interferometer driven by a quantum pump, analyzing flux dependence, oscillations, temperature effects, and dephasing mechanisms.

Contribution

It provides a detailed analysis of flux-dependent and independent currents, including their oscillations, temperature suppression, and effects of inelastic dephasing in a quantum pump-driven interferometer.

Findings

Flux-dependent current oscillates with frequency and is suppressed by temperature.

Flux-independent current oscillates with frequency and increases linearly with it.

Dephasing via a voltage probe suppresses certain current components depending on probe relaxation time.

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 non-adiabatic, 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.