Specific heat measurements of a superconducting NbS2 single crystal in an external magnetic field: Energy gap structure

Article

关键词: DEPENDENT SUPERCONDUCTIVITY;    2H-NBSE2;    INTERCALATION;   

DOI  :  10.1103/PhysRevB.82.014518

来源: SCIE

【 摘 要 】

The heat capacity of a 2H-NbS2 single crystal has been measured by a highly sensitive ac technique down to 0.6 K and in magnetic fields up to 14 T. At very low temperatures, data show excitations over an energy gap (2 Delta(S)/k(B)T(c)approximate to 2.1) much smaller than the BCS value. The overall temperature dependence of the electronic specific heat C-e can be explained either by the existence of a strongly anisotropic single-energy gap or within a two-gap scenario with the large gap about twice bigger than the small one. The field dependence of the Sommerfeld coefficient gamma shows a strong curvature for both principal-field orientations, parallel (H parallel to c) and perpendicular (H perpendicular to c) to the c axis of the crystal, resulting in a magnetic field dependence of the superconducting anisotropy. These features are discussed in comparison to the case of MgB2 and to the data obtained by scanning-tunneling spectroscopy. We conclude that the two-gap scenario better describes the gap structure of NbS2 than the anisotropic s-wave model.

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