Odd Viscosity and Odd Elasticity

TL;DR

This paper reviews materials exhibiting unconventional linear responses called odd viscosity and odd elasticity, highlighting their phenomenology, diverse systems, and microscopic origins, challenging traditional notions of elasticity and viscosity.

Contribution

It provides a comprehensive overview of odd elasticity and odd viscosity, including their phenomenology, occurrence in various systems, and microscopic mechanisms, which is novel in the field.

Findings

Identification of transverse responses and topological waves.

Discussion of odd viscosity and elasticity in diverse systems.

Insights into microscopic mechanisms behind odd responses.

Abstract

Elasticity typically refers to a material's ability to store energy, while viscosity refers to a material's tendency to dissipate it. In this review, we discuss fluids and solids for which this is not the case. These materials display additional linear response coefficients known as odd viscosity and odd elasticity. We first introduce odd elasticity and odd viscosity from a continuum perspective, with an emphasis on their rich phenomenology, including transverse responses, modified dislocation dynamics, and topological waves. We then provide an overview of systems that display odd viscosity and odd elasticity. These systems range from quantum fluids, to astrophysical gasses, to active and driven matter. Finally, we comment on microscopic mechanisms by which odd elasticity and odd viscosity arise.