Charge-density-wave mechanism in the 2H-NbSe2 family: Angle-resolved photoemission studies - art. no. 235101

We report high-resolution angle resolved photoemission studies of 2H-NbSe2 and 2H-TaS2. Results are compared to those of 2H-TaSe2. We find that the no rmal stare electronic structures in this family of materials have the same basic characteristics. Their Fermi surface consists of a pocket around Gamm a and another one around K. They ail exhibit a saddle band near EF along T- K. A finite energy gap is observed in the saddle band region and on the Fer mi surface around K in 2H-TaS2 and 2H-TaSe2. Gapping on the Fermi surface a round Gamma was not observed. We suggest that the charge density waves in t his family of materials originate from a combination of the partial nesting of the Fermi surface around K and the saddle band.