Pressure-Induced Valence Crossover in Superconducting CeCu2Si2

J.-P. Rueff; S. Raymond; M. Taguchi; M. Sikora; J.-P. Itié; F. Baudelet; D. Braithwaite; G. Knebel; D. Jaccard

doi:10.1103/PhysRevLett.106.186405

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Pressure-Induced Valence Crossover in Superconducting CeCu2Si2

J.-P. Rueff, S. Raymond, M. Taguchi, M. Sikora, J.-P. Itié, F. Baudelet, D. Braithwaite, G. Knebel, D. Jaccard

DOI 10.1103/PhysRevLett.106.186405 · Physical Review Letters

T1

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Abstract

Measurement of the Ce valence in the heavy fermion CeCu2Si2 is reported for the first time under pressure and at low temperature (T=14 K) in proximity of the superconducting region. CeCu2Si2 is considered as a strong candidate for a new type of pairing mechanism related to critical valence fluctuations which could set in at high pressure in the vicinity of the second superconducting dome. A quantitative estimate of the valence in this pressure region was achieved from the measurements of the Ce L3 edge in the high-resolution partial-fluorescence yield mode and subsequent analysis of the spectra within the Anderson impurity model. While a clear increase of the Ce valence is found, the weak electron transfer and the continuous valence change under pressure suggests a crossover regime with the hypothetical valence line terminating at a critical end point Tcr close to zero.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
CeCu2Si2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown