Current Noise in Quantum Point Contacts

TL;DR

This study measures current noise in quantum point contacts under various conditions, revealing how shot noise and electron heating relate to conductance features and magnetic fields, advancing understanding of quantum transport phenomena.

Contribution

It provides detailed experimental data on current noise behavior in quantum point contacts, including the effects of bias, magnetic field, and temperature, with comparison to phenomenological models.

Findings

Shot noise asymmetry relates to the 0.7 conductance structure.

High magnetic field restores spin-resolved transmission signatures.

Finite-bias noise includes device-specific electron heating effects.

Abstract

We present measurements of current noise in quantum point contacts as a function of source-drain bias, gate voltage, and in-plane magnetic field. At zero bias, Johnson noise provides a measure of the electron temperature. At finite bias, shot noise at zero field exhibits an asymmetry related to the 0.7 structure in conductance. The asymmetry in noise evolves smoothly into the symmetric signature of spin-resolved electron transmission at high field. Comparison to a phenomenological model with density-dependent level splitting yields quantitative agreement. Additionally, a device-specific contribution to the finite-bias noise, particularly visible on conductance plateaus (where shot noise vanishes), agrees quantitatively with a model of bias-dependent electron heating.