Spontaneous spin polarization in quantum point contacts

TL;DR

This study demonstrates that quantum point contacts in p-type GaAs/AlGaAs heterostructures exhibit spontaneous spin polarization at low conductance levels, especially when the 0.7 conductance anomaly is well-defined.

Contribution

It introduces a magnetic focusing technique to directly measure spin polarization in quantum point contacts, revealing spontaneous polarization in p-type heterostructures.

Findings

Finite spin polarization observed at conductance <2e^2/h

Polarization is enhanced in samples with a clear 0.7 structure

Method provides direct spatial spin separation measurement

Abstract

We use spatial spin separation by a magnetic focusing technique to probe the polarization of quantum point contacts. The point contacts are fabricated from p-type GaAs/AlGaAs heterostructures. A finite polarization is measured in the low-density regime, when the conductance of a point contact is tuned to <2e^2/h. Polarization is stronger in samples with a well defined ``0.7 structure''