Cooperative electron-phonon interaction in molecular chains

TL;DR

This paper develops an analytic model for cooperative strong electron-phonon interactions in molecular chains, revealing distinct behaviors in rings with odd and even numbers of sites and identifying a transition to a conducting charge density wave state.

Contribution

It introduces a new analytic model for cooperative electron-phonon interactions in Jahn-Teller systems, highlighting differences between odd and even site rings and their phase transitions.

Findings

Odd-site rings belong to a different universality class.

Even-site rings exhibit a transition to a conducting CDW state.

The model involves next-nearest-neighbor hopping and nearest-neighbor repulsion.

Abstract

Using a controlled analytic treatment, we derive a model that generically describes cooperative strong electron-phonon interaction (EPI) in one-band and two-band Jahn-Teller (JT) systems. The model involves a {\em next-nearest-neighbor} hopping and a nearest-neighbor repulsion. Rings with odd number of sites (o-rings) belong to a different universality class compared to rings with even number (e-rings). The e-rings, upon tuning repulsion, undergo a dramatic discontinuous transition to a {\em conducting commensurate} charge density wave (CDW) state with a period independent of filling.