Mesoscopic phase behavior in a quantum dot around crossover between single-level and multilevel transport regimes

TL;DR

This study investigates the mesoscopic phase behavior in a quantum dot during the transition from single-level to multilevel transport, revealing the absence of universal phase lapses in standard quantum dots with multiple Coulomb peaks.

Contribution

The paper presents experimental measurements of transmission phase in a quantum dot across the crossover regime, demonstrating mesoscopic behavior and challenging the universality of phase lapses.

Findings

Mesoscopic phase behavior observed in the crossover regime.

Universal phase lapses are absent in standard quantum dots.

Multiple Coulomb peaks are associated with non-universal phase shifts.

Abstract

The transmission phase across a quantum dot (QD) is expected to show mesoscopic behavior, where the appearance of a phase lapse between Coulomb peaks (CPs) as a function of the gate voltage depends on the orbital parity relation between the corresponding CPs. On the other hand, such mesoscopic behavior has been observed only in a limited QD configuration (a few-electron and single-level transport regime) and universal phase lapses by $\pi$ between consecutive CPs have been reported for all the other configurations. Here, we report on the measurement of a transmission phase across a QD around the crossover between single-level and multilevel transport regimes employing an original two-path quantum interferometer. We find mesoscopic behavior for the studied QD. Our results show that the universal phase lapse, a longstanding puzzle of the phase shift, is absent for a standard QD, where several tens of successive well-separated CPs are observed.