Dephasing in Mach-Zehnder interferometer by an Ohmic contact

TL;DR

This paper investigates how an Ohmic contact affects dephasing in a quantum Hall Mach-Zehnder interferometer, revealing conditions under which phase coherence is preserved or decays, depending on bias and temperature.

Contribution

It demonstrates that phase coherence can be maintained at low bias and temperature, and describes the decay behavior at high bias in a quantum Hall interferometer with Ohmic contact.

Findings

Phase coherence persists at low bias and temperature, saturating the visibility.

Visibility decays as a power law at high bias.

The free fermion picture applies when bias and temperature are below the charging energy.

Abstract

We study dephasing in an electronic Mach-Zehnder (MZ) interferometer based on quantum Hall (QH) edge states by a micromiter-sized Ohmic contact embedded in one of its arms. We find that at the filling factor $\nu=1$, as well as in the case where an Ohmic contact is connected to an MZ interfeoremter by a quantum point contact (QPC) that transmits only one electron channel, the phase coherence may not be fully suppressed. Namely, if the voltage bias $\Delta \mu$ and the temperature $T$ are small compared to the charging energy of the Ohmic contact $E_C$, the free fermion picture is manifested, and the visibility saturates at its maximum value. At large biases, $\Delta \mu \gg E_C$, the visibility decays in a power-law manner.