Avoided Valence Transition in a Plutonium Superconductor

Abstract

Some of the most remarkable phenomena---and greatest theoretical challenges---in condensed matter physics arise when $d$ or $f$ electrons are neither fully localized around their host nuclei, nor fully itinerant. This localized/itinerant "duality" underlies the correlated electronic states of the high-$T_c$ cuprate superconductors and the heavy-fermion intermetallics, and is nowhere more apparent than in the $5f$ valence electrons of plutonium. Here we report the full set of symmetry-resolved elastic moduli of $PuCoG{a}_5$---the highest $T_c$ superconductor of the heavy fermions ($T_c$=18.5 K)---and find that the bulk modulus softens anomalously over a wide range in temperature above $T_c$. Because the bulk modulus is known to couple strongly to the valence state, we propose that plutonium valence fluctuations drive this elastic softening. This elastic softening is observed to disappear when the superconducting gap opens at $T_c$, suggesting that plutonium valence fluctuations have a strong footprint on the Fermi surface, and that $PuCoG{a}_5$ avoids a valence-transition by entering the superconducting state. These measurements provide direct evidence of a valence instability in a plutonium compound, and suggest that the unusually high-$T_c$ in this system is driven by valence fluctuations.

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References in corpus (7)

• What is the valence of a correlated solid? The double life of delta-plutonium
• Signatures of valence fluctuations in CeCu2Si2 under high pressure
• Heavy electrons and the symplectic symmetry of spin
• Supplementary material to Heavy electrons and the symplectic symmetry of spin
• Crystal-field and Kondo scale investigation of CeMIn5 (M=Co, Ir and Rh): a combined x-ray absorption and inelastic neutron study
• Experimental observables near a nematic quantum critical point in the pnictide and cuprate superconductors
• Possibility of valence-fluctuation mediated superconductivity in Cd-doped CeIrIn${}_5$ probed by In-NQR

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