Intrinsic thermodynamic properties of the pyrochlore superconductor RbOs2O6 extracted by condensation energy analysis

Abstract

We develop a general procedure for the analysis of bulk thermodynamic data of a superconductor for samples containing a metallic non-superconducting second phase. The method is based on the condensation energy and it allows the extraction of the intrinsic properties of a superconductor even for non-ideal samples. Applying this procedure to the recently discovered geometrically frustrated beta-pyrochlore superconductor RbOs2O6 (Tc = 6.4 K) yields a Sommerfeld coefficient as high as 79 mu J/g/K^2 (44 mJ/mol_f.u./K^2). RbOs2O6 is inferred to be a strong type-II superconductor (kappa(Tc) = 23) in the intermediate-coupling regime similar to niobium (lambda_ep \approx 1). From the upper critical field mu_0 H_c2 \approx 6 T at 0 K, we estimate a Ginzburg-Landau coherence length xi \approx 74 AA. The condensation energy is 860 mu J/g (483 mJ/mol_f.u.) resulting in 1/(8 pi) (gamma_1 Tc^2)/DeltaU_1 \approx 0.15, a value well in the range of conventional phonon-mediated superconductors. The superconducting electronic specific heat indicates conventional s-wave pairing. The experimental Sommerfeld coefficient of 44 mJ/mol_f.u./K^2 is about 4 times larger than the one found in band structure calculations. Together with the electron-phonon coupling constant lambda_ep \approx 1 this leaves an additional lambda_add \approx 2.4 for enhancement due to other mechanisms.

arXiv commentSubmitted to Physical Review B

References in corpus (12)

• Superconductivity at 1 K in Cd2Re2O7
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• Superconductivity in the Correlated Pyrochlore Cd_2Re_2O_7
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Cited by in corpus (9)

• Rattling-Induced Superconductiviy in the Beta-Pyrochlore Oxides AOs2O6
• Mass enhancement, correlations, and strong coupling superconductivity in the beta-pyrochlore KOs2O6
• Thermal Conductivity of the Pyrochlore Superconductor KOs2O6: Strong Electron Correlations and Fully Gapped Superconductivity
• Study of the magnetic penetration depth in RbOs_2O_6
• Neutron Scattering Study of the Localized Mode in the beta-Pyrochlore Superconductors AOs2O6
• Superconducting Transition in the $\beta$-Pyrochlore AOs${}_2$O${}_6$ (A=Cs, Rb, K) under Pressure
• Structural and Superconducting Properties of RbOs2O6 Single Crystals
• Superconductivity and Rattling under High Pressure in the beta-Pyrochlore Oxide RbOs2O6
• Large mass enhancement in RbOs2O6