Probing the superconducting ground state near the charge density wave phase transition in Cu_0.06 TiSe₂

We have investigated the nature of the superconducting ground state of Cu_0.06TiSe₂ using muon spin rotation and muon spin relaxation measurements. The temperature dependence of the magnetic penetration depth of Cu_0.06TiSe₂ 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_B T_C] =2.5. The estimated magnetic penetration depth, λ, and the coherence length, ξ, 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, σsc (T), indicating the presence of strong pinning in Cu_0.06TiSe 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.