Unexpected finite-bias visibility dependence in an electronic Mach Zehnder interferometer

TL;DR

This paper investigates the unexpected asymmetry in interference visibility in an electronic Mach-Zehnder interferometer, revealing that the effect depends on the combined properties of the device rather than individual quantum point contacts.

Contribution

It uncovers a novel finite-bias dependence of interference visibility in an electronic Mach-Zehnder interferometer, showing the effect is an inherent property of the device, not just a single contact characteristic.

Findings

Visibility can increase with bias voltage under certain conditions.

The effect is independent of individual quantum point contact transmission.

Asymmetry depends on the combined transmission probabilities and magnetic field direction.

Abstract

We use an electronic Mach-Zehnder interferometer to explore the non-equilibrium coherence of the electron waves within the edge-states that form in the integral quantum Hall effect. The visibility of the interference as a function of bias-voltage and transmission probabilities of the mirrors, which are realized by quantum point-contacts, reveal an unexpected asymmetry at finite bias when the transmission probability $T$ of the mirror at the input of the interferometer is varied between 0 and 100%, while the transmission probability of the other mirror at the output is kept fixed. This can lead to the surprising result of an increasing magnitude of interference with increasing bias-voltage for certain values of $T$. A detailed analysis for various transmission probabilities and different directions of the magnetic field demonstrates that this effect is not related to the transmission characteristics of a single quantum point contact, but is an inherent property of the Mach-Zehnder interferometer with edge-states.