Density-driven higher-order topological phase transitions in amorphous solids

TL;DR

This paper demonstrates a density-driven transition from trivial to higher-order topological phases in amorphous 2D systems, characterized by corner states and quantized quadrupole moments, with implications for 3D amorphous materials.

Contribution

It introduces a novel density-driven phase transition mechanism for higher-order topological states in amorphous systems, expanding understanding beyond crystalline materials.

Findings

Topological trivial phase at low density

Transition to higher-order topological phase with increasing density

Size dependence of the phase transition

Abstract

Amorphous topological states, which are independent of the specific spatial distribution of microscopic constructions, have gained much attention. Recently, higher-order topological insulators, which are a new class of topological phases of matter, have been proposed in amorphous systems. Here, we propose a density-driven higher-order topological phase transition in a two-dimensional amorphous system. We demonstrate that the amorphous system hosts a topological trivial phase at low density. With an increase in the density of lattice sites, the topological trivial phase converts to a higher-order topological phase characterized by a quantized quadrupole moment and the existence of topological corner states. Furthermore, we confirm that the density-driven higher-order topological phase transition is size dependent. In addition, our results should be general and equally applicable to three-dimensional amorphous systems. Our findings may greatly enrich the study of higher-order topological states in amorphous systems.