Jahn-Teller polarons and their superconductivity in a molecular conductor

TL;DR

This paper proposes a theoretical mechanism where Jahn-Teller polarons induce high-temperature superconductivity in molecular conductors, with transition temperatures potentially reaching 100 K, and predicts a novel Mott insulating state at specific electron fillings.

Contribution

It introduces a new model linking Jahn-Teller polarons to superconductivity and predicts high transition temperatures in molecular conductors, including a novel Mott insulator phase.

Findings

Superconductivity up to 100 K is possible via Jahn-Teller polaron interactions.

A novel Mott insulator state occurs with two electrons per site.

Effective polaron-polaron attraction can lead to superconductivity in molecular conductors.

Abstract

We present a theoretical study of a possibility of superconductivity in a three dimensional molecular conductor in which the interaction between electrons in doubly degenerate molecular orbitals and an {\em intra}molecular vibration mode is large enough to lead to the formation of $E\otimes \beta$ Jahn-Teller small polarons. We argue that the effective polaron-polaron interaction can be attractive for material parameters realizable in molecular conductors. This interaction is the source of superconductivity in our model. On analyzing superconducting instability in the weak and strong coupling regimes of this attractive interaction, we find that superconducting transition temperatures up to 100 K are achievable in molecular conductors within this mechanism. We also find, for two particles per molecular site, a novel Mott insulating state in which a polaron singlet occupies one of the doubly degenerate orbitals on each site. Relevance of this study in the search for new molecular superconductors is pointed out.