Origin of the 0.25-anomaly in the nonlinear conductance of a quantum point contact

TL;DR

This paper uses non-equilibrium Green's functions within the Hartree approximation to explain the 0.25-anomaly and related conductance features in quantum point contacts, aligning theoretical results with experimental observations.

Contribution

It provides a quantitative theoretical explanation for the 0.25-anomaly in quantum point contact conductance using non-equilibrium Green's functions and non-linear screening effects.

Findings

Reproduces the 0.25-anomaly in differential conductance.

Explains upward bending of higher conductance plateaus.

Links features to non-linear screening and pinning effects.

Abstract

We calculate the non-linear conductance of a quantum point contact using the non-equilibrium Greens function technique within the Hartree approximation of spinless electrons. We quantitative reproduce the 0.25-anomaly in the differential conductance (i.e. the lowest plateau at 0.25-0.3*2e^2/h) as well as an upward bending of higher conductance half-integer plateaus seen in the experiments, and relate these features to the non-linear screening and pinning effects.