Optical absorption of non-interacting tight-binding electrons in a Peierls-distorted chain at half band-filling

In this first of three articles on the optical absorption of electrons in half-filled Peierls-distorted chains we present analytical results for non-interacting tightbinding electrons. We carefully derive explicit expressions for the current operator, the dipole transition matrix elements, and the optical absorption for electrons with a cosine dispersion relation of band width W and dimerization parameter δ. New correction (“η”-)terms to the current operator are identified. A broad band-to-band transition is found in the frequency range Wδ < ω < W whose shape is determined by the joint density of states for the upper and lower Peierls subbands and the strong momentum dependence of the transition matrix elements. PACS1996: 71.20.Rv, 71.10.Ca, 36.20.Kd ∗e-mail: [email protected] 1