Probing the superconducting ground state near the charge density wave phase transition inCu0.06TiSe2

Abstract

We have investigated the nature of the superconducting ground state of ${\text{Cu}}_{0.06}{\text{TiSe}}_{2}$ using muon spin rotation and muon spin relaxation measurements. The temperature dependence of the magnetic penetration depth of ${\text{Cu}}_{0.06}{\text{TiSe}}_{2}$ is consistent with a single gap $s$-wave BCS superconductor in the clean limit. The gap energy is $\ensuremath{\Delta}(0)=0.27(1)\text{ }\text{meV}$, which corresponds to a gap to ${T}_{C}$ ratio of $[2\ensuremath{\Delta}(0)/{k}_{B}{T}_{C}]=2.5$. The estimated magnetic penetration depth, $\ensuremath{\lambda}$, and the coherence length, $\ensuremath{\xi}$, 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, ${\ensuremath{\sigma}}_{sc}(T)$, indicating the presence of strong pinning in ${\text{Cu}}_{0.06}{\text{TiSe}}_{2}$. 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.