Tailoring Quadrupole Topological Insulators with Periodic Driving and Disorder

TL;DR

This paper explores how periodic driving and disorder can induce and protect quadrupole topological insulator phases, revealing new mechanisms for designing higher-order topological states in quantum materials.

Contribution

It demonstrates that disorder combined with periodic driving can create and stabilize quadrupole topological insulators, expanding the understanding of symmetry-protected higher-order topological phases.

Findings

Floquet QTI phase emerges from trivial band structures under elliptically polarized irradiation.

Disorder and periodic driving together can induce a QTI phase from a trivial static system.

Particle-hole symmetry protects the quadrupole topological insulator.

Abstract

The quadrupole topological insulator (QTI) has attracted intense studies as a prototype of symmetry-protected higher-order topological phases of matter with a quantized quadrupole moment. The realization of QTIs has been reported in various static settings with periodic structures. Here, we theoretically investigate topological phase transitions and establish the QTI phase in a periodically driven system with disorder. In the clean limit, the Floquet QTI phase emerges from a topologically trivial band structure driven by elliptically polarized irradiation. More strikingly, starting from a pure and static system with trivial topology, we unveil an intriguing QTI phase which necessitates the simultaneous presence of disorder and periodic driving. Furthermore, we reveal that particle-hole symmetry is sufficient to protect the QTI. Our work not only establishes a new strategy to design QTIs but also enriches the symmetry-protected mechanism of higher-order topology.