The influence of the interchain coupling on large acoustic polarons in coupled molecular chains: Three coplanar parallel molecular chains

We study the properties of the single large adiabatic polaron in the substances composed of three parallel equally separated coplanar molecular chains. Particular attention has been devoted to the influence of the interchain coupling strength on polaron stability in order to elucidate the origin of the large polaron existence, which, contrary to the predictions of continuum adiabatic theories may persist in realistic conditions. Our results indicate the existence of the effectively two-dimensional stationary polarons with comparably large longitudinal radius while the transverse one ranges from zero, in the absence of interchain coupling, to approximately twice of the interchain separation when coupling strength tends towards the infinity. These two-dimensional polarons are both energetically and dynamically stable. This is quite the opposite to the expectations based on the traditional adiabatic large polaron theories which, in the case of short ranged electron phonon interaction, predict that the stable large polaron may exist only in 1D systems. Stability of these 2D polarons increases with the increase of the interchain coupling strength so that they may be comparably more stable than the pure 1D polarons. (C) 2015 Elsevier Ltd. All rights reserved.