Plasmon Evolution and Charge-Density Wave Suppression in Potassium   Intercalated Tantalum Diselenide
  We have investigated the influence of potassium intercalation on the formation of the charge-density wave (CDW) instability in 2H-tantalum diselenide by means of Electron Energy-Loss Spectroscopy and density functional theory. Our observations are consistent with a filling of the conduction band as indicated by a substantial decrease of the plasma frequency in experiment and theory. In addition, elastic scattering clearly points to a destruction of the CDW upon intercalation as can be seen by a vanishing of the corresponding superstructures. This is accompanied by a new superstructure, which can be attributed to the intercalated potassium. Based on the behavior of the c-axis upon intercalation we argue in favor of interlayer-sites for the alkali-metal and that the lattice remains in the 2H-modification. 
A. K\"onig (1), K. Koepernik (1), R. Schuster (1), R. Kraus (1), M.   Knupfer (1), B. B\"uchner (1), H. Berger (2) ((1) IFW ...
cond-mat.str-el