Anisotropic odd viscosity in chiral active fluids

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• Anton Souslov, University of Bath
• Tuesday 15 October 2019, 13:00-14:00
• MR11, CMS.

If you have a question about this talk, please contact Etienne Fodor.

Chiral active fluids are materials composed of self-spinning rotors that continuously inject energy and angular momentum at the microscale. Out-of-equilibrium fluids with active-rotor constituents have been experimentally realised using nanoscale biomolecular motors, microscale active colloids, or macroscale driven chiral grains. I will discuss how chiral active fluids break both parity and time-reversal symmetries in their steady states, giving rise to dissipationless linear-response coefficients in the viscosity tensor, collectively called odd (equivalently, Hall) viscosity. I will then discuss how spatially anisotropic viscous coefficients and stresses can be designed by applying a time-modulated drive. If the drive induces a rotation whose rate is slowed down when the constituents point along specific directions, anisotropic structures and mechanical responses arise at long timescales. Classical fluids with internal torques can display additional components of the odd viscosity neglected in previous studies of quantum Hall fluids that assumed angular momentum conservation. These anisotropic and angular momentum-violating odd-viscosity coefficients can change even the bulk flow of an incompressible fluid by acting as a source of vorticity. In addition, shear distortions in the shape of an inclusion result in torques.

1. A. Souslov, A. Gromov, V. Vitelli. Anisotropic odd viscosity via time-modulated drive. arXiv:1909.08505 (2019)

2. D. Banerjee, A. Souslov, A. G. Abanov, V. Vitelli. Odd viscosity in chiral active fluids. Nat. Commun. 8, 1573 (2017)

This talk is part of the DAMTP Statistical Physics and Soft Matter Seminar series.

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