Magnetic Moment Formation in Quantum Point Contacts

TL;DR

This paper investigates the conditions under which local magnetic moments form in quantum point contacts using a Hubbard-like model, analytical susceptibility calculations, and phase diagrams to understand stability and formation criteria.

Contribution

It introduces a combined numerical and analytical approach to determine magnetic moment formation in quantum point contacts, including phase diagrams and stability analysis.

Findings

Magnetic moments form under specific Coulomb and gate voltage conditions.

Analytical susceptibility calculations provide explicit formation criteria.

Point contact stability depends on dimensions and potential parameters.

Abstract

We study the formation of local magnetic moments in quantum point contacts. Using a Hubbard-like model to describe point contacts formed in a two dimensional system, we calculate the magnetic moment using the unrestricted Hartree approximation. We analyze different type of potentials to define the point contact, for a simple square potential we calculate a phase diagram in the parameter space (Coulomb repulsion - gate voltage). We also present an analytical calculation of the susceptibility to give explicit conditions for the occurrence of a local moment, we present a simple scaling argument to analyze how the stability of the magnetic moment depends on the point contact dimensions.