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arXiv · 0712.2939

Experimental evidence for a two-gap structure of superconducting NbSe_2: a specific heat study in external magnetic fields

C. L. Huang·J. -Y. Lin·Y. T. Chang·C. P. Sun·H. Y. Shen·C. C. Chou·H. Berger·T. K. Lee·H. D. Yang
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Abstract

To resolve the discrepancies of the superconducting order parameter in quasi-two-dimensional NbSe_2, comprehensive specific-heat measurements have been carried out. By analyzing both the zero-field and mixed-state data with magnetic fields perpendicular to and parallel to the c axis of the crystal and using the two-gap model, we conclude that (1) more than one energy scale of the order parameter is required for superconducting NbSe_2 due to the thermodynamic consistency; (2)delta_L=1.26 meV and delta_S=0.73 meV are obtained; (3) N_S(0)/N(0)=11%~20%; (4) The observation of the kink in gamma(H) curve suggests that the two-gap scenario is more favorable than the anisotropic s-wave model to describe the gap structure of NbSe_2; and (5)delta_S is more isotropic and has a three-dimensional-like feature and is located either on the Se or the bonding Nb Fermi sheets.

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C. L. Huang, J. -Y. Lin, Y. T. Chang, C. P. Sun, H. Y. Shen, C. C. Chou, H. Berger, T. K. Lee, H. D. Yang. 2007-12-18. Experimental evidence for a two-gap structure of superconducting NbSe_2: a specific heat study in external magnetic fields. https://doi.org/10.1103/physrevb.76.212504

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