The odd free surface flows of a colloidal chiral fluid

In simple fluids, such as water, invariance under parity and time-reversal symmetry imposes that the rotation of constituent ‘atoms’ is determined by the flow and that viscous stresses damp motion. Activation of the rotational degrees of freedom of a fluid by spinning its atomic building blocks brea...

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Bibliographic Details
Published in:Nature physics 2019-11, Vol.15 (11), p.1188-1194
Main Authors: Soni, Vishal, Bililign, Ephraim S., Magkiriadou, Sofia, Sacanna, Stefano, Bartolo, Denis, Shelley, Michael J., Irvine, William T. M.
Format: Article
Language:English
Subjects:
639/301/923/614
639/766/189
Atomic
Classical and Continuum Physics
Complex Systems
Computational fluid dynamics
Condensed Matter Physics
Fluid flow
Fluid mechanics
Fluids
Free surfaces
Hydrodynamics
Magnets
Mathematical and Computational Physics
Molecular
Optical and Plasma Physics
Physics
Physics and Astronomy
Surface dynamics
Surface waves
Theoretical
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Summary:In simple fluids, such as water, invariance under parity and time-reversal symmetry imposes that the rotation of constituent ‘atoms’ is determined by the flow and that viscous stresses damp motion. Activation of the rotational degrees of freedom of a fluid by spinning its atomic building blocks breaks these constraints and has thus been the subject of fundamental theoretical interest across classical and quantum fluids. However, the creation of a model liquid that isolates chiral hydrodynamic phenomena has remained experimentally elusive. Here, we report the creation of a cohesive two-dimensional chiral liquid consisting of millions of spinning colloidal magnets and study its flows. We find that dissipative viscous ‘edge-pumping’ is a key and general mechanism of chiral hydrodynamics, driving unidirectional surface waves and instabilities, with no counterpart in conventional fluids. Spectral measurements of the chiral surface dynamics suggest the presence of Hall viscosity, an experimentally elusive property of chiral fluids. Precise measurements and comparison with theory demonstrate excellent agreement with a minimal chiral hydrodynamic model, paving the way for the exploration of chiral hydrodynamics in experiment. A chiral fluid comprising spinning colloidal magnets exhibits macroscopic dynamics reminiscent of the free surface flows of Newtonian fluids, together with unique features suggestive of Hall—or odd—viscosity.
ISSN:1745-2473
1745-2481
DOI:10.1038/s41567-019-0603-8