LANDAU DAMPING AND LIFTING OF VIBRATIONAL DEGENERACY IN METALLIC POTASSIUM FULLERIDE

Raman spectra are presented for single crystal metallic potassium full eride at low temperatures. As compared to the undoped material dramati c changes in line position (Delta omega greater than or equal to 80 cm (-1)) and linewidth (gamma greater than or equal to 60 cm(-1)), partic ularly for the two highest and the two lowest H-g modes, were observed . The lowest frequency H-g modes were found to be asymmetric but struc tured and could be fitted with five components which exhibit a line sh ift-linewidth relation. The experimental results are discussed in a mo del of single-particle excitation (Landau damping). Electron-phonon co upling constants lambda(i) were determined for all eight H-g modes usi ng Alien's formula. The total for all lambda(i) was found to be 0.9 fo r a density of states at the Fermi level of 12 eV(-1).