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The Helical Liquid and the Edge of Quantum Spin Hall Systems

Congjun Wu·B. Andrei Bernevig·Shou-Cheng Zhang
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Abstract

The edge states of the recently proposed quantum spin Hall systems constitute a new symmetry class of one-dimensional liquids dubbed the ``helical liquid'', where the spin orientation is determined by the direction of electron motion. We prove a no-go theorem which states that a helical liquid with an odd number of components cannot be constructed in a purely 1D lattice system. In a helical liquid with an odd number of components, a uniform gap in the ground state can appear when the time-reversal (TR) symmetry is spontaneously broken by interactions. On the other hand, a correlated two-particle backscattering term by an impurity can become relevant while keeping the TR invariance. The Kondo effect in such a liquid exhibits new features in the structure of the screening cloud.

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Congjun Wu, B. Andrei Bernevig, Shou-Cheng Zhang. 2006-02-27. The Helical Liquid and the Edge of Quantum Spin Hall Systems. https://doi.org/10.1103/physrevlett.96.106401

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