Non-universal transmission phase behaviour of a large quantum dot

TL;DR

This study measures the transmission phase in a large quantum dot with hundreds of electrons, revealing both phase lapses and plateaus, and shows how quantum dot deformation influences phase behavior, advancing understanding of quantum dot transmission.

Contribution

It provides the first detailed experimental observation of transmission phase behavior in a large quantum dot, demonstrating the impact of quantum dot deformation on phase sequences.

Findings

Observed both phase lapses and plateaus across multiple resonances.

Quantum dot deformation modifies the sequence of phase behaviors.

Demonstrated the influence of quantum dot parity on phase modifications.

Abstract

The electron wave function experiences a phase modification at coherent transmission through a quantum dot. This transmission phase undergoes a characteristic shift of $\pi$ when scanning through a Coulomb-blockade resonance. Between successive resonances either a transmission phase lapse of $\pi$ or a phase plateau is theoretically expected to occur depending on the parity of the corresponding quantum dot states. Despite considerable experimental effort, this transmission phase behaviour has remained elusive for a large quantum dot. Here we report on transmission phase measurements across such a large quantum dot hosting hundreds of electrons. Using an original electron two-path interferometer to scan the transmission phase along fourteen successive resonances, we observe both phase lapses and plateaus. Additionally, we demonstrate that quantum dot deformation alters the sequence of transmission phase lapses and plateaus via parity modifications of the involved quantum dot states. Our findings set a milestone towards a comprehensive understanding of the transmission phase of quantum dots.