Ferromagnetic Spin Coupling as the Origin of 0.7 Anomaly in Quantum Point Contacts

TL;DR

This paper investigates the 0.7 conductance anomaly in quantum point contacts, proposing it arises from ferromagnetic spin interactions and fluctuations affecting electron transport.

Contribution

It introduces a model linking ferromagnetic spin coupling to the 0.7 anomaly, supported by quantum Monte Carlo conductance calculations.

Findings

0.7 anomaly results from strong ferromagnetic fluctuations.

Conductance plateau appears due to incoherent scattering at high temperature.

Electron traversal time matches ferromagnetic excitation timescale.

Abstract

We study one-dimensional itinerant electron models with ferromagnetic coupling to investigate the origin of 0.7 anomaly in quantum point contacts. Linear conductance calculations from the quantum Monte Carlo technique for spin interactions of different spatial range suggest that $0.7(2e^{2}/h)$ anomaly results from a strong interaction of low-density conduction electrons to ferromagnetic fluctuations formed across the potential barrier. The conductance plateau appears due to the strong incoherent scattering at high temperature when the electron traversal time matches the time scale of dynamic ferromagnetic excitations.