Effects of spin-orbit interaction and crystal fields on superconductingP-wave pair states and their collective excitations in cubic systems

Pair states do not necessarily transform as the basis functions of the irreducible representations of the relevant point group, when quartic terms in the Ginzburg-Landau free energy are taken into account. The number of states with nodes in the quasiparticle energy spectrum is thus reduced. The spin-orbit interaction and crystal-field effects give rise to new low-frequency collective modes, which could be responsible for the peaks in the acoustic attenuation observed just below $T_c$.