新鲜和老化超导体PuCoGa $_5$中超流密度的μ子自旋旋转测量
Muon spin rotation measurements of the superfluid density in fresh and aged superconducting PuCoGa$_5$
摘要：
为了研究序参量的对称性，并研究老化对放射性材料超导性质的影响，我们利用μ子自旋旋转技术测量了超流密度$ρ_{\rm s}(T)$的温度依赖性和大小，通过磁场在PuCoGa $_5$中的穿透深度$λ(T)$（名义临界温度$T_{c0} = 18.5$ K）.在室温下老化25天（$T_c = 18.25$ K）和400天（$T_c = 15.0$ K）后测量相同的单晶。超流密度的温度依赖性很好地描述了在这两种材料的模型，使用d-波间隙对称性。与新鲜样品相比，老化样品中的μ子自旋弛豫速率$σ$的幅度$σ\propto 1/λ^2\proptoρ_s/m^*$（其中$m^*$是有效质量）降低了约70%。这表明自辐照诱导缺陷的散射不处于传统Abrikosov-Gor'kov对破缺理论的极限，而是处于短相干长度（PuCoGa $_5$中约2 nm）超导性的极限。
英文摘要：
We have measured the temperature dependence and magnitude of the superfluid density $ρ_{\rm s}(T)$ via the magnetic field penetration depth $λ(T)$ in PuCoGa$_5$ (nominal critical temperature $T_{c0} = 18.5$ K) using the muon spin rotation technique in order to investigate the symmetry of the order parameter, and to study the effects of aging on the superconducting properties of a radioactive material. The same single crystals were measured after 25 days ($T_c = 18.25$ K) and 400 days ($T_c = 15.0$ K) of aging at room temperature. The temperature dependence of the superfluid density is well described in both materials by a model using d-wave gap symmetry. The magnitude of the muon spin relaxation rate $σ$ in the aged sample, $σ\propto 1/λ^2\proptoρ_s/m^*$, where $m^*$ is the effective mass, is reduced by about 70% compared to fresh sample. This indicates that the scattering from self-irradiation induced defects is not in the limit of the conventional Abrikosov-Gor'kov pair-breaking theory, but rather in the limit of short coherence length (about 2 nm in PuCoGa$_5$) superconductivity.
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