Temperature Modulation of the Transmission Barrier in Quantum Point Contacts

TL;DR

This study models ballistic transport through a quantum point contact in GaAs/AlGaAs heterojunctions, revealing how temperature and barrier shape influence transmission, with implications for understanding electron interactions in nanoscale devices.

Contribution

It introduces a 3D quantum-mechanical variational model that accounts for temperature effects and barrier shape on QPC transmission, advancing theoretical understanding of electron transport.

Findings

Transmission shoulder depends on QPC length and barrier profile

Temperature smears out the transmission features

Antiferromagnetic interactions enhance the transmission shoulder

Abstract

We investigate near-equilibrium ballistic transport through a quantum point contact (QPC) along a GaAs/AlGaAs heterojunction with a transfer matrix technique, as a function of temperature and the shape of the potential barrier in the QPC. Our analysis is based on a three-dimensional (3D) quantum-mechanical variational model within the Hartree-Fock approximation that takes into account the vertical depletion potential from ionized acceptors in GaAs and the gate-induced transverse confinement potential that reduce to an effective slowly-varying one-dimensional (1D) potential along the narrow constriction. The calculated zero-temperature transmission exhibits a shoulder ranging from 0.3 to 0.6 depending on the length of the QPC and the profile of the barrier potential. The effect is a consequence of the compressibility peak in the 1D electron gas and is enhanced for anti-ferromagnetic interaction among electrons in the QPC, but is smeared out once temperature is increased by a few tenths of a kelvin.