Measurement of the Transmission Phase through a Quantum Dot Embedded in One Arm of an Electronic Mach-Zehnder Interferometer

TL;DR

This study measures the transmission phase shift in a quantum dot embedded in an electronic Mach-Zehnder interferometer, revealing phase changes associated with quantum dot resonances in a quantum Hall system.

Contribution

It provides experimental insights into the phase behavior of quantum dots within an interferometer, highlighting the effects of unintended quantum dot formation on interference.

Findings

Resonances cause a π phase shift in the interference pattern.

Quantum dots form due to electrostatic potential superposition and disorder.

High visibility interference observed in the quantum Hall regime.

Abstract

We investigate an electronic Mach-Zehnder interferometer with high visibility in the quantum Hall regime. The superposition of the electrostatic potentials from a quantum point contact (QPC) and the residual disorder potential from doping impurities frequently results in the formation of inadvertent quantum dots (QD) in one arm of the interferometer. This gives rise to resonances in the QPC transmission characteristics. While crossing the QD resonance in energy, the interferometer gains a phase shift of $\pi$ in the interference pattern.