UNUSUAL PLASMON DISPERSION IN THE QUASI-ONE-DIMENSIONAL CONDUCTOR (TASE4)(2)I - EXPERIMENT AND THEORY

We present a combined experimental and theoretical study of the plasmo n dispersion in a quasi-one-dimensional conductor, the transition meta l tetrachalco-halogenide (TaSe4)(2)I. The dispersion relation, as meas ured by electron energy-loss spectroscopy in transmission, is quasilin ear, which is not expected from the literature. However. we show that the data can be explained within a one-band model, which additionally allows the derivation of the conduction-band dispersion. Thus, contrar y to evidence from photoemission measurements, we find no hint for sin gular properties caused by one dimensionality.