The anisotropy of the upper critical field Hc2and electrical resistivity in 2H-NbS₂

The anisotropy of the upper critical fields H c2 parallel and perpendicular to the layer planes of 2H-NbS 2 in investigated in the temperature range between 1.2 K and T c =5.95 K in magnetic fields up to 8 T. The ratio H c2 ///H c2 perpendicular to increases from 3.5 at the reduced temperature T/T c approximately 1 to a value of 5.5 at T/T c =0.4. H(T) c23 // shows the expected upward curvature close to T c indicating a quasi-two-dimensional behaviour. For the first time the authors report on the anisotropy of the ideal resistivities in the normal state up to 300 K. Close to T c the anisotropy rho 3 / rho 1 is approximately 7200 and decreases to a value of 2140 at room temperature. It is suggested that anisotropic electron-phonon scattering might explain the temperature dependence on the ideal anisotropy, and together with a small inter-layer coupling energy accounts for the high anisotropy.