Finite-bias visibility dependence in an electronic Mach-Zehnder interferometer

We use an electronic Mach-Zehnder interferometer to explore the nonequilibrium coherence of the electron waves within the edge states that form in the integral quantum-Hall-effect device. The visibility of the interference as a function of bias voltage and transmission probabilities of the mirrors, which are realized by quantum point contacts, reveals 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. .