Nonlinear Physics Seminar:"Active fluids with odd viscosity"

Wed, 15/01/202012:00-13:30
Danciger B building, Seminar room
Lecturer: Anton Souslov, University of Bath in the UK
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 such 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 this model, odd-viscous coefficients depend on the nonlinear, dissipative response of the underlying fluid of rods, i.e., odd viscosity is not simply given by angular momentum density.
[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).