Electron-electron interaction effects in quantum point contacts

TL;DR

This paper investigates how electron-electron interactions affect conductance, shot noise, and thermopower in quantum point contacts, explaining phenomena like the 0.7 anomaly through perturbative and nonperturbative methods.

Contribution

It provides a comprehensive analysis of interaction effects on quantum point contact conductance, including a self-consistent nonperturbative approach and realistic potential estimates.

Findings

Interaction causes conductance suppression with temperature and voltage.

Magnetic field reduces interaction effects due to Pauli principle.

Conductance saturates at high temperatures, aligning with experimental data.

Abstract

We consider electron-electron interaction effects in quantum point contacts on the first quantization plateau, taking into account all scattering processes. We compute the low-temperature linear and nonlinear conductance, shot noise, and thermopower, by perturbation theory and a self-consistent nonperturbative method. On the conductance plateau, the low-temperature corrections are solely due to momentum-nonconserving processes that change the relative number of left- and right-moving electrons. This leads to a suppression of the conductance for increasing temperature or voltage. The size of the suppression is estimated for a realistic saddle-point potential, and is largest in the beginning of the conductance plateau. For large magnetic field, interaction effects are strongly suppressed by the Pauli principle, and hence the first spin-split conductance plateau has a much weaker interaction correction. For the nonperturbative calculations, we use a self-consistent nonequilibrium Green's function approach, which suggests that the conductance saturates at elevated temperatures. These results are consistent with many experimental observations related to the so-called 0.7 anomaly.