Plasmon excitations in quasi-one-dimensional K0.3MoO3

We present an investigation of the plasmon excitations in a quasi-one-dimen sional metal, the blue bronze K0.3MoO3. The dispersion relation along the o ne-dimensional direction, as measured by electron energy-loss spectroscopy in transmission, is quasilinear over a wide momentum range before it exhibi ts a negative curvature. We show that the quasilinear part can be explained within an essentially three-dimensional model based on the random-phase ap proximation. Band-structure effects are thereby considered through the Ehre nreich-Cohen formula, tailor-made to the specific, strongly anisotropic mat erial. From this analysis, we find no hint for exceptional properties cause d by one dimensionality as is currently discussed in the context of photoem ission measurements. The genuine dependence of the plasmon modes on the pro pagation angle relative to the one-dimensional axis is masked by interband transitions lying at about the same energy as the plasmon excitations itsel f.