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Phase diagram of two interacting helical states

Santos, R.A., Gutman, D.B., Carr, S.T. (2016) Phase diagram of two interacting helical states. Physical Review B: Condensed Matter and Materials Physics, 93 (23). Article Number 235436. ISSN 0163-1829. (doi:10.1103/PhysRevB.93.235436) (KAR id:59748)

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We consider two coupled time-reversal-invariant helical edge modes of the same helicity, such as would occur on two stacked quantum spin Hall insulators. In the presence of interaction, the low-energy physics is described by two collective modes, one corresponding to the total current flowing around the edge and the other one describing relative fluctuations between the two edges.We find that quite generically, the relative mode becomes gapped at low temperatures, but only when tunneling between the two helical modes is nonzero. There are two distinct possibilities for the gapped state depending on the relative size of different interactions. If the intraedge interaction is stronger than the interedge interaction, the state is characterized as a spin-nematic phase. However,

in the opposite limit, when the interaction between the helical edge modes is strong compared to the interaction within each mode, a spin-density wave forms, with emergent topological properties. First, the gap protects the conducting phase against localization by weak nonmagnetic impurities; second, the protected phase hosts localized zero modes on the ends of the edge that may be created by sufficiently strong nonmagnetic impurities.

Item Type: Article
DOI/Identification number: 10.1103/PhysRevB.93.235436
Uncontrolled keywords: Physics of Quantum Materials
Subjects: Q Science
Divisions: Faculties > Sciences > School of Physical Sciences
Depositing User: Michael Woods
Date Deposited: 20 Dec 2016 13:43 UTC
Last Modified: 16 Sep 2020 15:17 UTC
Resource URI: (The current URI for this page, for reference purposes)
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