Evidence for Helical Nuclear Spin Order in GaAs Quantum Wires

TL;DR

This study provides transport evidence for helical nuclear spin order in GaAs quantum wires, showing conductance behavior consistent with theoretical predictions of nuclear magnetism in a Luttinger liquid.

Contribution

First experimental evidence supporting helical nuclear spin order in GaAs quantum wires through transport measurements.

Findings

Conductance drops from 2 e^2/h to 1 e^2/h at low temperatures.

Conductance becomes temperature-independent below 0.1 K.

Results align with theoretical models of helical nuclear magnetism.

Abstract

We present transport measurements of cleaved edge overgrowth GaAs quantum wires. The conductance of the first mode reaches 2 e^2/h at high temperatures T > 10 K, as expected. As T is lowered, the conductance is gradually reduced to 1 e^2/h, becoming T-independent at T < 0.1 K, while the device cools far below 0.1 K. This behavior is seen in several wires, is independent of density, and not altered by moderate magnetic fields B. The conductance reduction by a factor of two suggests lifting of the electron spin degeneracy in absence of B. Our results are consistent with theoretical predictions for helical nuclear magnetism in the Luttinger liquid regime.