Measuring the macroscopic angular momentum in ³He-A via superfluid sound

A (quasi) two dimensional chiral superfluid is expected to carry chiral current of Majorana fermions along its edge. This chiral edge current is thought to be responsible for the macroscopic orbital angular momentum (MOAM) predicted in the superfluid. However, neither the chiral current nor the MOAM has been experimentally confirmed directly. In this talk, we present a new experimental approach in which we create a substantial coupling between the chiral current and the third sound of superfluid 3He. The third sound of superfluid 3He distorts the free surface which induces the chiral current to flow along the entire surface instead of confined on the edge. A large spatial overlap between the chiral current on the surface and the third sound modes manifests a significant frequency shift on these modes of about 1%. This frequency shift can be read out using techniques developed in superfluid optomechanics.