In quantum wires, the hyperfine coupling between conduction electrons and nuclear spins can lead to a (partial) ordering of both of them at low temperatures. By an interaction-enhanced mechanism, the nuclear spin order, caused by RKKY exchange, acts back onto the electrons and gaps out part of their spectrum. In wires with two subbands characterized by distinct Fermi momenta kF1 and kF2, the nuclear spins form a superposition of two helices with pitches {\pi}/kF1 and {\pi}/kF2, thus exhibiting a beating pattern. This order results in a reduction of the electronic conductance in two steps upon lowering the temperature.
@article{arxiv.1303.1542,
title = {Helical nuclear spin order in two-subband quantum wires},
author = {Tobias Meng and Daniel Loss},
journal= {arXiv preprint arXiv:1303.1542},
year = {2013}
}
Comments
20 pages, 9 figures. Version as published with minor modification as compared to v1 (some short discussions in the introduction and summary, and one figure, have been added)