Abstract
Hydrodynamics is shown to induce non-Hermitian topological phenomena in ordinary, passive soft matter. This is demonstrated by subjecting a two-dimensional 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. An 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.
Highlights
The conservation of energy in isolated Hermitian systems is a basic tenet of physics, but in practice, most systems are open, exchanging energy and information with the external world
This inherent non-Hermiticity is traditionally seen as an inevitable imperfection of realistic systems, yet recent studies revealed that it gives rise to distinctive phenomena unmatched in Hermitian physics [1]—most notably skewed spectral bands prone to symmetry breaking when exceptional points emerge [2,3,4,5,6]
To see how non-Hermitian topology arises in ordinary elastic matter at low-Reynolds number, consider the following model system [Fig. 1(a)]
Summary
The conservation of energy in isolated Hermitian systems is a basic tenet of physics, but in practice, most systems are open, exchanging energy and information with the external world This inherent non-Hermiticity is traditionally seen as an inevitable imperfection of realistic systems, yet recent studies revealed that it gives rise to distinctive phenomena unmatched in Hermitian physics [1]—most notably skewed spectral bands prone to symmetry breaking when exceptional points emerge [2,3,4,5,6]. The present study gives a clear positive answer: A simple model and simulations demonstrate non-Hermitian topological hallmarks in standard, passive elastic networks subject to ordinary viscous flow [22,23] Such settings are omnipresent in the overdamped low-Reynolds regime, typical in cells, macromolecules, and simple soft matter systems, suggesting. In the Discussion, we suggest possible experimental realizations and examine potential implications and future directions
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