Topological waves in fluids with odd viscosity

Understand

Fluids in which both time-reversal and parity are broken can display a dissipationless viscosity that is odd under each of these symmetries.

• Here, we show how this odd viscosity has a dramatic effect on topological sound waves in fluids, including the number and spatial profile of topological edge modes.
• Odd viscosity provides a short-distance cutoff that allows us to define a bulk topological invariant on a compact momentum space.
• As the sign of odd viscosity changes, a topological phase transition occurs without closing the bulk gap.