Experimental evidence for a two-gap structure of superconducting Nb Se2: 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 Nb Se2, comprehensive specific-heat measurements have been carried out. By analyzing both the zero-field and mixed-state data with magnetic fields perpendicular (H c) to and parallel (H c) 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 Nb Se2 due to the thermodynamic consistency; (2) ΔL =1.26 meV and ΔS =0.73 meV are obtained; (3) NS (0) N (0) =11%-20%; (4) the observation of the kink in γ (H) curve suggests that the two-gap scenario is more favorable than the anisotropic s -wave model to describe the gap structure of Nb Se2; and (5) ΔS is more isotropic and has a three-dimensional-like feature and is located either on the Se or the bonding Nb Fermi sheets.

Original languageEnglish
Article number212504
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume76
Issue number21
DOIs
Publication statusPublished - 2007 Dec 13

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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