Instabilities in Half-Filled One-Dimensional Systems: Valence Bond Analysis

Abstract

Theoretical investigations on one-dimensional (1D) half-filled systems started many years ago, yet they still attract considerable attention, due to the wide variety of properties and phenomena discovered in the continuously growing family of synthetic 1D compounds, such as charge transfer (CT) salts, 1D polymers or mixed valence inorganic chains.1 In this paper we focus attention on the ground state instabilities of chains with alternating or uniform on-site energy, by analyzing the interplay between the electronic kinetic energy and several types of interactions, namely, the electron-electron (e-e) one (both intra- and intersite), the electron-molecular vibration (e-mv) and the electron- lattice phonon (e-lph) couplings. To our knowledge none of the so far proposed theoretical models has simultaneously taken into account all the above interactions.