Exchange and correlation effects in the transmission phase through a few-electron quantum dot

TL;DR

This paper investigates how electron interactions, shape, and density influence the transmission phase in few-electron quantum dots, explaining complex experimental behaviors through advanced calculations and the Friedel sum rule.

Contribution

It combines configuration-interaction calculations with the Friedel sum rule to explain the non-universal phase behavior in quantum dots with few electrons, highlighting the effects of Coulomb interaction and correlations.

Findings

Phase evolution depends on dot shape and electron density for more than two electrons.

No phase lapse occurs when transitioning from one to two electrons.

Significant phase shifts occur in the Coulomb and Kondo regimes for strongly correlated dots.

Abstract

The transmission phase through a quantum dot with few electrons shows a complex, non-universal behavior. Here we combine configuration-interaction calculations ---treating rigorously Coulomb interaction--- and the Friedel sum rule to provide a rationale for the experimental findings. The phase evolution for more than two electrons is found to strongly depend on dot's shape and electron density, whereas from one to two the phase never lapses. In the Coulomb (Kondo) regime the phase shifts are significant fractions of pi (pi/2) for the second and subsequent charge addition if the dot is strongly correlated. These results are explained by the proper inclusion in the theory of Coulomb interaction, spin, and orbital degrees of freedom.