Electron transport through quantum wires and point contacts

TL;DR

This study uses advanced computational methods to analyze electron transport in quantum wires, revealing conductance behavior similar to experimental 0.7-anomaly due to spin polarization effects.

Contribution

It introduces a mean-field model with Green's function and density-functional theory to simulate conductance in quantum wires, capturing the 0.7-anomaly phenomenon.

Findings

Observation of a conductance plateau at 0.7G_0 in short wires.

Temperature and wire length influence conductance similarly to experimental data.

Spontaneous spin polarization explains the 0.7-anomaly in the model.

Abstract

We have studied quantum wires using the Green's function technique and the density-functional theory, calculating the electronic structure and the conductance. All the numerics are implemented using the finite-element method with a high-order polynomial basis. For short wires, i.e. quantum point contacts, the zero-bias conductance shows, as a function of the gate voltage and at a finite temperature, a plateau at around 0.7G_0. (G_0 = 2e^2/h is the quantum conductance). The behavior, which is caused in our mean-field model by spontaneous spin polarization in the constriction, is reminiscent of the so-called 0.7-anomaly observed in experiments. In our model the temperature and the wire length affect the conductance-gate voltage curves in the same way as in the measured data.