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Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 53: Superconductivity: Fe-based Superconductors - 122

TT 53.3: Talk

Wednesday, April 2, 2014, 10:00–10:15, HSZ 201

Superconducting specific heat jump Δ CTcβ (β ∼ 2) and gapless Fermi surfaces in K1−xNaxFe2As2 — •V. Grinenko1, D.V. Efremov1, S.-L. Drechsler1, S. Aswartham1, D. Gruner1, M. Roslova1, I. Morozov1, K. Nenkov1, S. Wurmehl1,2, A.U.B. Wolter1, B. Holzapfel1,3, and B. Büchner1,21Leibniz-Institute for Solid State and Materials Research, IFW-Dresden, D-01171 Dresden, Germany — 2Institut für Festkörperphysik, TU Dresden, Germany — 3Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

We present a systematic study of the electronic specific heat jump (Δ Cel) at the superconducting transition temperature Tc of K1−xNaxFe2As2. Both Tc and Δ Cel monotonously decrease with increasing x. The jump scales approximately with a novel power-law: Δ CelTcβ with β ≈ 2 determined by the impurity scattering rate. This finding is in sharp contrast to most of all iron-pnictide superconductors with a cubic Bud’ko-Ni-Canfield (BNC) scaling. Our observations, also, suggests that disorder diminishes the small gaps leading to partial gapless superconductivity which results in a large residual Sommerfeld coefficient in the superconducting state for x > 0. Both T-dependence of Cel(T) in the superconducting state and the nearly quadratic scaling of Δ Cel at Tc are well described by the Eliashberg-theory for a single-band d-wave superconductor with weak pair-breaking due to nonmagnetic impurities having reduced the density of superconducting quasi-particles.

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