Chiral Lattice Supersolid on Edges of Quantum Spin Hall Samples

TL;DR

This paper proposes that the edges of Quantum Spin Hall insulators can host a novel chiral lattice supersolid phase due to competing spin interactions, offering a new platform for studying supersolidity.

Contribution

It introduces a mechanism for realizing a chiral lattice supersolid on the edges of topological insulators through competing spin interactions and magnetic frustration.

Findings

Spontaneous breaking of parity at zero temperature.

Formation of a chiral lattice supersolid phase.

Potential for experimental observation of supersolidity.

Abstract

We show that edges of Quantum Spin Hall topological insulators represent a natural platform for realization of exotic supersolid phase. On one hand, fermionic edge modes are helical due to the nontrivial topology of the bulk. On the other hand, a disorder at the edge or magnetic adatoms may produce a dense array of localized spins interacting with the helical electrons. The spin subsystem is magnetically frustrated since the indirect exchange favors formation of helical spin order and the direct one favors (anti)ferromagnetic ordering of the spins. At a moderately strong direct exchange, the competition between these spin interactions results in the spontaneous breaking of parity and in the Ising type order of the $z$-components at zero temperature. If the total spin is conserved the spin order does not pin a collective massless helical mode which supports the ideal transport. In this case, the phase transition converts the helical spin order to the order of a chiral lattice supersolid. This represents a radically new possibility for experimental studies of the elusive supersolidity.