Two Mott Insulator Theory of Superconductivity in K$_3$X (X: picene, .. p-terphenyl, .. C$_{60}$)

TL;DR

This paper proposes a unified Mott insulator framework for superconductivity in K$_3$X compounds, involving RVB states, charge transfer, and Josephson coupling, suggesting potential for room temperature superconductivity.

Contribution

It introduces a novel theory combining Mott insulators, RVB states, and charge transfer to explain superconductivity in aromatic hydrocarbons and fullerenes, with implications for high Tc.

Findings

Charged RVB states in X$^{2-}$ molecules act as Cooper pair boxes.

Weak Josephson coupling creates a Bose Mott insulator with high Tc potential.

Charge transfer and doping induce superconductivity in the Mott insulators.

Abstract

We look for unifying aspects behind superconductivity in aromatic hydrocarbon and fullerene family K$_3$X (X: picene, .. p-terphenyl, .. C$_{60}$). Aromatic hydrocarbon molecules support RVB states. Consequent stability (aromaticity) makes them reluctant electron acceptors. We argue that X accepts only two (not all three) electrons from K$_3$ and creates charged RVB's in X$^{2-}$, and becomes a (molecular) Cooper pair box. A weak Josephson coupling between X$^{2-}$ molecules creates a Bose Mott insulator, a potential high Tc superconductor. Remaining lone electron in the complex (K$_3)^{2+}$ occupies a suitable metal orbital hybrid. They hybridize weakly through X$^{2-}$ molecular bridges, to form a half filled band of renormalized K atom orbitals, a Fermionic Mott insulator. An interplay of RVB physics and charge transfer (mutual doping) or external doping leads to superconductivity in one or both Mott insulators. In our theory there is room for room temperature superconductivity.