Plasmon evolution and charge-density wave suppression in potassium intercalated 2H-TaSe ₂

We have investigated the influence of potassium intercalation on the formation of the charge-density wave (CDW) instability in 2 H -TaSe 2 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 2 H modification.