Transmission phase of a singly occupied quantum dot in the Kondo regime

TL;DR

This study measures the transmission phase of a quantum dot in the Kondo regime, confirming theoretical predictions and revealing phase behavior across different coupling regimes and temperatures.

Contribution

First experimental measurement of the transmission phase in a single-electron quantum dot within the Kondo regime, validating theoretical models.

Findings

Transmission phase reaches c/2 in the Kondo regime.

Phase reaches c in the Coulomb blockade regime.

Temperature has little effect on phase behavior between 30-600 mK.

Abstract

We report on the phase measurements on a quantum dot containing a single electron in the Kondo regime. Transport takes place through a single orbital state. Although the conductance is far from the unitary limit, we measure for the first time, a transmission phase as theoretically predicted of \pi/2. As the dot's coupling to the leads is decreased, with the dot entering the Coulomb blockade regime, the phase reaches a value of \pi. Temperature shows little effect on the phase behaviour in the range 30--600 mK, even though both the two-terminal conductance and amplitude of the Aharonov-Bohm oscillations are strongly affected. These results confirm that previous phase measurements involved transport through more than a single level.