Abstract
We investigated the effect of enhancement of superconducting transition temperature by nonmagnetic atom disorder in the series of filled skutterudite-related compounds (LaSn, CaRhSn, YRhSn, LuRhSn; Co, Ru, Rh), where the atomic disorder is generated by various defects or doping. We have shown that the disorder on the coherence length scale in these nonmagnetic quasiskutterudite superconductors additionally generates a non-homogeneous, high-temperature superconducting phase with (dilute disorder scenario), while the strong fluctuations of stoichiometry due to increasing doping can rapidly increase the superconducting transition temperature of the sample even to the value of (dense disorder leading to strong inhomogeneity). This phenomenon seems to be characteristic of high-temperature superconductors and superconducting heavy fermions, and recently have received renewed attention. We experimentally documented the stronger lattice stiffening of the inhomogeneous superconducting phase in respect to the bulk one and proposed a model that explains the behavior in the series of nonmagnetic skutterudite-related compounds.
Highlights
The effect of atomic disorder on superconducting properties has been the cause of intense research, both experimental and theoretical, since the BCS theory [1] explained the mechanism of superconductivity
We point out the unique behavior observed for the skutterudite-related compounds whereby lattice disorder enhances the superconducting transition temperature the heat capacity (Tc) to Tc?, where Tc? > Tc
It has been shown that their superconducting transition temperature Tc depends on the degree of atomic disorder in the system, and that Tc increases with random disorder
Summary
The effect of atomic disorder on superconducting properties has been the cause of intense research, both experimental and theoretical, since the BCS theory [1] explained the mechanism of superconductivity. Even a small amount of magnetic dopants can drastically reduce the critical temperature of the superconducting state [5,6]. Later it was documented experimentally and by theory, that the Anderson theorem does not hold true in a strongly disordered nonmagnetic superconducting system. Y5 Rh6 Sn18 and Lu5 Rh6 Sn18 quasiskutterudites have been reported as s-wave BCS superconductors with atomic-scale disorder, which generates a novel superconducting state with critical temperature. We discuss the known theoretical models describing the temperature dependencies of the upper critical fields Hc2 , obtained experimentally for various skutterudite-related components of the series. Depending on the degree of disorder, we prove the correctness of the Werthamer–Helfand–Hohenberg theory or the percolation model, both of which are considered within the dirty limit of the BCS superconductor
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