Wilson ratio in Yb-substituted CeCoIn₅

Author： Capan C. Seyfarth G. Hurt D. Prevost B. Roorda S. Bianchi A. D. Fisk Z.

E-ISSN： 1286-4854|92|4|47004-47004

ISSN： 0295-5075

Source： EPL (EUROPHYSICS LETTERS), Vol.92, Iss.4, 2010-12, pp. : 47004-47004

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Abstract

We have investigated the effect of Yb substitution on the Pauli-limited, heavy-fermion superconductor, CeCoIn₅. Yb acts as a non-magnetic divalent substituent for Ce throughout the entire doping range, equivalent to hole doping on the rare-earth site. We found that the upper critical field in (Ce,Yb)CoIn₅ is Pauli limited, yet the reduced (H,T) phase diagram is insensitive to disorder, as expected in the purely orbitally limited case. We use the Pauli-limiting field, the superconducting condensation energy and the electronic specific-heat coefficient to determine the Wilson ratio (R_W), the ratio of the specific-heat coefficient to the Pauli susceptibility in CeCoIn₅. The method is applicable to any Pauli-limited superconductor in the clean limit.