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|Title:||Discovery of Two New Pu-based Superconductors - PuCoIn5 and PuRhIn5|
|Authors:||BAUER E.d.; ALTARAWNEH M. M.; TOBASH Paul Henry; GOFRYK Krzysztof; AYALA-VALENZUELA O. E.; MITCHELL J. N.; MCDONALD R. D.; MIELKE C. H.; RONNING F; GRIVEAU Jean-Christophe; COLINEAU Eric; ELOIRDI Rachel; CACIUFFO Roberto; SCOTT B. L.; JANKA O.; KAUZLARICH S. M.; THOMPSON J.d.|
|Citation:||Plutonium Futures - the Science 2012|
|Publisher:||Plutonium Futures 2012|
|Type:||Articles in periodicals and books|
|Abstract:||Since the discovery of unconventional superconductivity at 18.5 K in PuCoGa5 and at 8.7 K in PuRhGa5, attention has been focused on understanding the origin of the high transition temperatures, which are an order of magnitude higher than all other Ce- or U-based heavy fermion superconductors. The most common scenario proposed is that superconductivity arises from an abundance of antiferromagnetic (AFM) spin fluctuations caused by proximity to a zero-temperature, second-order antiferromagnetic transition, or quantum critical point (QCP). Investigations of the phase diagrams of the isostructural CeMIn5 (M=Co, Rh, Ir) family of heavy fermion superconductors, tuned either by pressure or chemical substitution, have established that these materials also reside close to an AFM QCP, in which an unusual normal state is characterized by a non-Fermi liquid temperature dependence of the electrical resistivity, i.e., ~Tn with n<2, instead of n=2 for a Fermi liquid. In both PuMGa5 (M=Co, Rh) superconductors, the powerlaw behavior of the spin-lattice relaxation rate 1/T1 ~ T1/3 indicate that spin fluctuations may dominate the physical properties near Tc.4,5 With this behavior and a non-Fermi liquid resistivity ~T4/3 (Ref. 2), it appears that the PuMGa5 materials may be near to a QCP, but the presumed antiferromagnetic state has not been found. Alternatively, superconductivity may be mediated by critical charge (valence) fluctuations. While examples are less common, experiments on CeCu2Si2 under pressure delineated a second, separate dome of superconductivity with a higher Tc (by a factor of 3-4) at higher pressure close to a valence instability, suggesting that the higher Tc superconductivity may be mediated by critical valence (charge) fluctuations, rather than by AFM spin fluctuations comprising the superconducting dome at lower pressure. We report the physical properties of two new superconductors, PuCoIn5 and PuRhIn5, the first In analogs of the "Pu115" family of superconductors.8 Two scenarios (Fig. 1) emerge from a comparison of PuMIn5 (M=Co, Rh) and PuCoGa5: 1) superconductivity arises from proximity to an AFM QCP in PuMIn5, while superconductivity in PuCoGa5 may instead be mediated by valence fluctuations (with its own distinct superconducting dome) as is found in CeCu2Si2 under pressure, or 2) the PuMX5 (X=Ga, In) materials reside on a common broad superconducting dome that is separate from antiferromagnetism ending in an AFM QCP, as has been found in CeIr(In1-xCdx)5.9 Work at Los Alamos National Laboratory (LANL) was performed under the auspices of the U.S. DOE, OBES, Division of Materials Sciences and Engineering and funded in part by the LANL Directed Research and Development program.|
|JRC Directorate:||Nuclear Safety and Security|
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