Fermion zero modes at the boundary of superfluid $^3$He-B

Superfluid $^3$He-B belongs to the important special class of time-reversal invariant topological superfluids. It has Majorana fermions as edge states on the surface of bulk $^3$He-B. On the rough wall these fermion zero modes have finite density of states at $E=0$. It is possible that Lancaster experiments with a wire vibrating in $^3$He-B have already probed Majorana fermions living on the surface of the wire.