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arXiv · 0706.4367

Muon spin rotation measurements of the superfluid density in fresh and aged superconducting PuCoGa$_5$

K. Ohishi·R. H. Heffner·G. D. Morris·E. D. Bauer·M. J. Graf·J. -X. Zhu·L. A. Morales·J. L. Sarrao·M. J. Fluss·D. E. MacLaughlin·L. Shu·W. Higemoto·T. U. Ito
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Abstract

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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K. Ohishi, R. H. Heffner, G. D. Morris, E. D. Bauer, M. J. Graf, J. -X. Zhu, L. A. Morales, J. L. Sarrao, M. J. Fluss, D. E. MacLaughlin, L. Shu, W. Higemoto, T. U. Ito. 2007-06-29. Muon spin rotation measurements of the superfluid density in fresh and aged superconducting PuCoGa$_5$. https://doi.org/10.1103/physrevb.76.064504

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