A Fermi Surface for2H−NbSe2

Abstract

Interlayer bonding splits the $z^2$ band of the $2H$ polytypes of layered metal dichalcogenides. In group-$\mathrm{V}A$ compounds hole surfaces may appear at the Fermi level, leading to two-carrier conduction. The low-temperature reversal of the Hall effect may be due to a shift of the Fermi energy which removes the holes. Intercalation fills the band structure to a level where such a transition would not occur.