Fermi liquid instabilities in the spin channel

We study the Fermi-surface instabilities of the Pomeranchuk type [Sov. Phys. JETP 8, 361 (1959)] in the spin-triplet channel with high orbital partial waves [F-l(a)(l>0)]. The ordered phases are classified into two classes, dubbed the alpha and beta phases by analogy to the superfluid He-3 A and B phases. The Fermi surfaces in the alpha phases exhibit spontaneous anisotropic distortions, while those in the beta phases remain circular or spherical with topologically nontrivial spin configurations in momentum space. In the alpha phase, the Goldstone modes in the density channel exhibit anisotropic overdamping. The Goldstone modes in the spin channel have a nearly isotropic underdamped dispersion relation at small propagating wave vectors. Due to the coupling to the Goldstone modes, the spin-wave spectrum develops resonance peaks in both the alpha and beta phases, which can be detected in inelastic neutron-scattering experiments. In the p-wave channel beta phase, a chiral ground-state inhomogeneity is spontaneously generated due to a Lifshitz-like instability in the originally nonchiral systems. Possible experiments to detect these phases are discussed.