Topology-induced phase transitions in quantum spin Hall lattices

TL;DR

This paper studies how topological phase transitions occur in quantum spin Hall lattices when their structure is deformed, revealing the fragility of the QSH phase and proposing experimental verification with cold atoms.

Contribution

It demonstrates the loss of QSH robustness under lattice deformations and proposes a method to verify these effects using cold atom systems with synthetic gauge fields.

Findings

QSH phase becomes less robust with added lattice sites

Topological phase transitions can be induced by lattice deformations

Experimental verification feasible with cold atom optical lattices

Abstract

Physical phenomena driven by topological properties, such as the quantum Hall effect, have the appealing feature to be robust with respect to external perturbations. Lately, a new class of materials has emerged manifesting their topological properties at room temperature and without the need of external magnetic fields. These topological insulators are band insulators with large spin-orbit interactions and exhibit the quantum spin-Hall (QSH) effect. Here we investigate the transition between QSH and normal insulating phases under topological deformations of a two-dimensional lattice. We demonstrate that the QSH phase present in the honeycomb lattice looses its robustness as the occupancy of extra lattice sites is allowed. Furthermore, we propose a method for verifying our predictions with fermionic cold atoms in optical lattices. In this context, the spin-orbit interaction is engineered via an appropriate synthetic gauge field.