Ferromagnetically coupled magnetic impurities in a quantum point contact

TL;DR

This paper explores how localized magnetic impurity states with ferromagnetic coupling form in quantum point contacts, explaining the coexistence of Kondo effects and spin filtering through exact diagonalization analysis.

Contribution

It reveals the formation of ferromagnetically coupled magnetic impurities in quantum point contacts, a novel insight into their electronic and magnetic properties.

Findings

Localized magnetic impurity states appear at conductance channel openings

These impurities exhibit stable ferromagnetic coupling

The results explain coexistence of Kondo correlation and spin filtering

Abstract

We investigate the ground and excited states of interacting electrons in a quantum point contact using exact diagonalization method. We find that strongly localized states in the point contact appear when a new conductance channel opens due to momentum mismatch. These localized states form magnetic impurity states which are stable in a finite regime of chemical potential and excitation energy. Interestingly, these magnetic impurities have ferromagnetic coupling, which shed light on the experimentally observed puzzling coexistence of Kondo correlation and spin filtering in a quantum point contact.