Electronic structure and Fermi-surface-related instabilities in1T−TaS2and1T−TaSe2

Abstract

The electronic-energy-band structure and full-Brillouin-zone Fermi surfaces of the layered dichalcogenides, $1T\ensuremath{-}\mathrm{T}\mathrm{a}{\mathrm{S}}_{2}$ and $1T\ensuremath{-}\mathrm{T}\mathrm{a}{\mathrm{Se}}_{2}$, have been calculated using the Korringa-Kohn-Rostoker method in the muffin-tin approximation. We find that the Fermi surfaces for both systems away from symmetry points and lines have cross sections which are approximately constant along the $z$ direction. Strong nesting features of the Fermi surface are found for a spanning vector parallel to the $\ensuremath{\Gamma}M$ direction in reciprocal space with values in good agreement with the charge-density-wave results found by Wilson, Di Salvo, and Mahajan for these compounds.