Electron-Phonon Interactions in Polyacene Organic Transistors

Abstract

We present a simple model for the electron-phonon interactions between the energy subbands in polyacene field-effect transistors and the vibrations of the crystal. We introduce a generalized Su-Schrieffer-Heeger model, arguing that the strongest electron-phonon interactions in these systems originate from the dependence of inter-molecule hopping amplitudes on collective molecular motion. We compute the electron-phonon spectral function $α^2F(ω)$ as a function of two-dimensional hole density and the coupling strength constant. Our results are in agreement with the sharp onset of superconductivity near half-filling discovered in recent experiments by Schön {\it et al.} [Batlogg] and predict an increase of $T_c$ with pressure. We further speculate on the implications that the observation of the quantum Hall effect in these systems has on the effective band mass in the low carrier density regime.