Electronic Pair-Binding and Hund's Rule Violations in Doped $C_{60}$

TL;DR

This study uses the $t$-$J$ model and density-matrix renormalization group to explore electronic properties of doped $C_{60}$, revealing Hund's rule violations and potential for electronic superconductivity.

Contribution

It demonstrates that doped $C_{60}$ can exhibit pair-binding and Hund's rule violations, suggesting a possible electronic mechanism for superconductivity.

Findings

Hund's rule is violated in doped $C_{60}$

Effective attraction (pair-binding) occurs at three added electrons

Electronic mechanism of superconductivity is plausible in doped $C_{60}$

Abstract

We calculate the electronic properties of the $t$-$J$ model on a $C_{60}$ molecule using the density-matrix renormalization group and show that Hund's first rule is violated and that for an average of three added electron per molecule, an effective attraction (pair-binding) arises for intermediate values of $t/J$. Specifically, it is energetically favorable to put four electrons on one $C_{60}$ and two on a second rather than putting three on each. Our results show that a dominantly electronic mechanism of superconductivity is possible in doped $C_{60}$.