Capillary waves on odd active fluids: broken reciprocity and nonlinear effects

Fluids comprised of active chiral particles can brake parity/time reversal symmetry, and thus can exhibit an antisymmetric viscous contribution – the odd viscosity. Further, it is known that odd fluids host non-reciprocal and non-linear modes [1]. Yet, most of the works on odd fluids have focused on bulk or interfacial problems, ignoring surface tension.

In this talk, we explore the behaviour of surface waves due to both odd viscosity and surface tension. We show that the disparate nature of right and left propagating modes breaks reciprocity [2]. Moreover, we go past the linear regime and explore the nonlinear effects introducing a nonlinear and nonlocal scalar model that captures the behaviour of the surface. With this, we show how the dispersive phenomena of odd viscosity and surface interact and how can in future be controlled with the design of active chiral fluids.

[1] P. Cosme, H. Terças, Phys. Rev. B 107, 195432, 2023

[2] H. du Plessis, P. Cosme, M. Jalaal, Non-Reciprocal Capillary Waves with Odd Viscosity, in preparation.