Regensburg 2025 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 24: Focus Session: Broken Symmetries in Statistical Physics - Dynamics of Odd Systems
DY 24.8: Talk
Wednesday, March 19, 2025, 17:15–17:30, H43
Vortex formation and odd viscosity in a chiral active fluid — •Joscha Mecke1,2, Yongxiang Gao1, Gerhard Gompper2, and Marisol Ripoll2 — 1Institute for Advanced Study, Shenzhen University, Shenzhen, PR China — 2Institute of Advanced Simulation, Forschungszentrum Jülich, Germany
Materials consisting of active particles with an intrinsic rotation can be considered as chiral active matter. We study a colloidal chiral active system, consisting of magnetic microrotors of diameter 0.8 μm in an externally applied rotating magnetic field. The stabilised colloids synchronously rotate with the rotating field and solely interact via steric and hydrodynamic interactions, granting odd and active stresses already at low densities and large colloidal separations. We address the system by means of experiments as well as particle based hydrodynamics simulations (MPC) of the active colloidal suspension. The rotors' transverse, anti-symmetric, and non-reciprocal interactions lead to a pair-rotation about the centre of mass and subsequently to the formation of multiscale vortices. Energy is injected on the particle level and is transported to the largest scales in the system, unless it is dissipated at a hydrodynamic damping length, a process reminiscent of turbulence, even in the absence of dominant inertial contributions. The rich phenomenology of our system additionally includes odd diffusion and enhancement of effective diffusive transport by the introduction of obstruction, directed transport by virtue of symmetry breaking at confining walls, and correlations between vorticity and density which allow for a measurement of the system's odd viscosity.
Keywords: chiral active matter; odd viscosity; active turbulence; colloidal rotors