Anisotropy of Upper Critical Field in Superconducting 2H-NbS2

Temperature and angular dependences of upper critical field H c 2 in layered superconductor 2 H -NbS 2 have been investigated. Parallel-to-perpendicular critical field ratio was found to be 7.5∼8.1 in the experimental temperature range of T =4.9∼5.8 K. The experimental results were found to be well described by 3-dimensional model for anisotropic superconductors. This value is much larger than 2.3∼3.2 found in 2 H -NbSe 2 . It is suggested that absence of CDW in 2 H -NbS 2 keeps anisotropy of the Fermi surface high down to low temperatures and this is responsible for the large anisotropy or the upper critical field in this material.