"Spiral Luttinger liquids: helical nuclear spin order, Rashba nanowires, and
their conductance"
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When taking into account the nuclear spins, a quantum wire is a finite size
Kondo lattice system. In such a system, the RKKY interaction can result in an
ordered state at low temperatures, in which the Kondo lattice spins form one or
several helices. These helices in turn induce a partial ordering of the
electrons, and open up gaps in their spectrum. The helical order is a relatively
stable phenomenon that persists even for multiple electronic subbands.
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The electrons in this state form a quasi-helical (or "spiral") Luttinger liquid,
equivalent to a Rashba nanowire in a magnetic field. (Quasi-) helical Luttinger
liquids have applications as spin filters or Cooper pair splitters, and are a
crucial ingredient for topological wires with Majorana end states. We discuss
experimental signatures of quasi-helical Luttinger liquids (both for Rashba
nanowires and ordered Kondo lattices), and find, for example, a non-universal
conductance that deviates from 1 e^2/h. This underlines that quasi-helical
systems differ from their ideal counterparts in experimentally important
quantities.