TRANSVERSE-WAVES IN SUPERFLUID HE-3-B

We examine the theory of collisionless transverse current waves in bulk superfluid He-3-B, including the coupling to the order parameter collective modes. At low frequencies, omega << DELTA(T), the order parameter modes do not contribute to the restoring force for a transverse current, and the quasiparticle contribution drops rapidly as the gap in the spectrum develops. Thus, low-frequency transverse sound becomes overdamped at temperatures near T(c). However, at low temperatures (T less than or similar 0.3T(c)) the off-resonant coupling to the J=2-, M=+/-1 modes stabilizes a propagating transverse current mode, with a large phase velocity and low damping for frequencies above a critical frequency that is approximately that of the J=2- mode. We also discuss the similarities and differences of longitudinal and transverse sound in the superfluid phases. For example, in zero field, right- and left-circularly polarized waves are degenerate. A magnetic field, with H over arrow pointing right parallel-to q over arrow pointing right, lifts this degeneracy, giving rise to the analog of circular dichroism and birefringence of electromagnetic waves. Thus, transverse waves may be more easily detected in the B-phase than in normal He-3.