Spin-Dependent Acoustic Response In The Nonunitary A(1) And A(2) Phases Of Superfluid He-3 Under High Magnetic Fields

The transverse acoustic impedance of superfluid He-3 was measured in the A(1) and A(2) phases up to 13 T to investigate the surface states in nonunitary superfluids. The temperature dependence of the impedance was much larger in the A(1) phase than in the A(2) phase. This nonsymmetric behavior indicates that momentum exchange with walls for spin-down surface states is quite different from that for spin-up surface states. The spin-dependent response might be a reflection of an essential feature of the nonunitary states where gap amplitudes depend on spin states. Weak-coupling theories ignore any spin-dependent processes and do not account for the nonsymmetric behavior.