Unconventional superconductivity and antiferromagnetic spin fluctuations in the heavy fermion compound CeCoIn5: 115In-NQR study under pressure

Abstract We report systematic evolution of superconducting (SC) characteristic of heavy-fermion superconductor CeCoIn 5 via the nuclear-quadrupole-resonance (NQR) measurement under pressure ( P ). The temperature dependence of nuclear spin–lattice relaxation rate (1/ T 1 ) below T C has revealed that once the value of SC energy gap (2 Δ 0 / k B T C ) slightly increases in P P , it decreases significantly. By contrast, T C increases monotonously up to 2.6 K as P increases up to 1 GPa, exhibiting a saturation in P =1.0–1.5 GPa.