Exotic Topology in Ordinary Soft Matter

TL;DR

This paper demonstrates that hydrodynamics can induce non-Hermitian topological phenomena in ordinary passive soft matter, revealing new topological features like bulk Fermi arcs and exceptional points in elastic lattices under viscous flow.

Contribution

It introduces the first demonstration of hydrodynamics-induced non-Hermitian topological phenomena in soft matter, combining analytic models and simulations.

Findings

Hydrodynamics causes Dirac cones to split into bulk Fermi arcs.

Exceptional points with opposite topological charges are paired.

Spectral bands exhibit van Hove singularity lines in the density of states.

Abstract

Hydrodynamics is shown to induce non-Hermitian topological phenomena in ordinary, passive soft matter. This is demonstrated for the first time by subjecting a 2D elastic lattice to a low-Reynolds viscous flow. The interplay of hydrodynamics and elasticity splits Dirac cones into bulk Fermi arcs, pairing exceptional points with opposite half-integer topological charges. The bulk Fermi arc is a generic hallmark of the system exhibited in all lattice and flow symmetries. Analytic model and simulations explain how the emergent singularities shape the spectral bands and give rise to a web of van Hove singularity lines in the density of states. The present findings suggest that non-Hermitian physics can be explored in a broad class of ordinary soft matter, living and artificial alike, opening avenues for topology-based technology in this regime.