Small $T_1^{-1}$ coherence peak near $T_c$ in unconventional superconductors

It is usually believed that a coherence peak just below T c in the nuclear spin lattice relaxation rate T − 1 1 in superconducting materials is a signature of conventional s-wave pairing. In this paper we demonstrate that any unconventional superconductor obeying BCS pure-case weak-coupling theory should show a small T − 1 1 coherence peak near T c , generally with a height between 3 and 15 percent greater than the normal state T − 1 1 at T c . It is largely due to impurity and magnetic effects that this peak has not commonly been observed. . no T c