The free surface of a colloidal chiral fluid: waves and instabilities from odd stress and Hall viscosity

Understand

In simple fluids, such as water, invariance under parity and time-reversal symmetry imposes that the rotation of constituent 'atoms' are 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 which 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.