Spatial structure of the superconducting phase in heavy-fermion systems and anomalies in the excitation spectrum

A degenerate superconducting phase in a metal with strong spin-orbital coupling may have a domain structure at low temperatures. The domain walls (of width ∼ξ=v_F/Δ₀) carry a finite density of states N(0)≈mk_f/π² per unit volume, which in turn results in the presence of a linear term γT in the electronic specific heat C_e(T). With the help of the Atiyah-Singer theorem, this can be proved for a wide class of domain structures.