Probing the superconducting ground state near the charge density wave phase transition in Cu_(0.06)TiSe_2

摘要

We have investigated the nature of the superconducting ground state of Cu_(0.06)TiSe_2 using muon spin rotation and muon spin relaxation measurements. The temperature dependence of the magnetic penetration depth of Cu_(0.06)TiSe_2 is consistent with a single gap s-wave BCS superconductor in the clean limit. The gap energy is Δ(0)=0.27(1) meV, which corresponds to a gap to T_C ratio of [2Δ(0)/k_BT_C]=2.5. The estimated magnetic penetration depth, λ, and the coherence length, ξ, are 660(10) and 15(5) ran, respectively. Furthermore, we observe an irreversibility line in the temperature dependence of the superconducting part of the muon relaxation rate, σ_(sc)(T), indicating the presence of strong pinning in Cu_(0.06)TiSe_2. 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.