Superconductivity and Magnetoresistance in NbSe2

Abstract

Electron conduction in single crystals of Nb${\mathrm{Se}}_{2}$ has been measured at 4.2\ifmmode^\circ\else\textdegree\fi{}K in magnetic fields up to 150 kOe. The upper critical field ${H}_{c2}$ has been measured as a function of the angle between the applied field and the layers of the crystal for currents flowing both parallel and perpendicular to the layers. An effective-mass model based on simple considerations of the anisotropy of the crystal has been used to obtain a value for the ratio of effective masses for electron motion parallel and perpendicular to the layers, and the best value obtained is $\frac{{m}_{\ensuremath{\parallel}}}{{m}_{\ensuremath{\perp}}}=0.09\ifmmode\pm\else\textpm\fi{}0.01$. Transverse-magnetoresistance rotation diagrams have been studied and structure due to flux flow and flux pinning has been observed.