Probing the superconducting ground state near the charge density wave phase transition in Cu0.06TiSe2

We have investigated the nature of the superconducting ground state of Cu0.06TiSe2 using muon spin rotation and muon spin relaxation measurements. The temperature dependence of the magnetic penetration depth of Cu0.06TiSe2 is consistent with a single gap s-wave BCS superconductor in the clean limit. The gap energy is Delta(0) = 0.27(1) meV, which corresponds to a gap to T-C ratio of [2 Delta(0)/k(B)T(C)] = 2.5. The estimated magnetic penetration depth, lambda, and the coherence length, zeta, are 660(10) and 15(5) nm, respectively. Furthermore, we observe an irreversibility line in the temperature dependence of the superconducting part of the muon relaxation rate, sigma(sc)(T), indicating the presence of strong pinning in Cu0.06TiSe2. Interestingly, at low temperatures we have found clear evidence of the presence of low-energy spin fluctuations that coexist with superconductivity and have an Arrhenius temperature dependence.