Engineering rich two-dimensional higher-order topological phases by flux and periodic driving

TL;DR

This paper introduces a method to engineer higher-order topological phases in two-dimensional systems using flux and periodic driving, revealing new types of nodal-line semimetals and topological insulators with tunable properties.

Contribution

It demonstrates flux-induced second-order nodal-line semimetals and topological insulators in 2D systems without traditional symmetries, and proposes Floquet engineering to create hybrid-order topological phases.

Findings

Discovery of flux-induced second-order nodal-line semimetals.

Proposal of Floquet scheme for hybrid-order topological phases.

Demonstration of tunable corner states and nodal-line structures.

Abstract

Nodal-line semimetals are commonly believed to exist in $\mathcal{PT}$ symmetric or mirror-rotation symmetric systems. Here, we find a flux-induced parameter-dimensional second-order nodal-line semimetal (SONLS) in a two-dimensional system without $\mathcal{PT}$ and mirror-rotation symmetries. It has coexisting hinge Fermi arcs and drumhead surface states. Meanwhile, we discover a flux-induced second-order topological insulator (SOTI). We then propose a Floquet engineering scheme to create exotic parameter-dimensional hybrid-order nodal-line semimetals with abundant nodal-line structures and widely tunable numbers of corner states in a SONLS and SOTI, respectively. Our results break the perception of SONLSs and supply a convenient way to artificially synthesize exotic topological phases by periodic driving.