Magnetic Properties of Undoped $C_{60}$

TL;DR

This paper investigates the magnetic properties of undoped C60 fullerenes using the Hubbard model, revealing an exotic ground state, a first-order phase transition, and implications for experimental verification.

Contribution

It introduces a detailed analysis of the magnetic behavior of C60 within the Hubbard model, highlighting the absence of phase transitions and the presence of a metamagnetic transition.

Findings

Exotic classical ground state with nontrivial topology

No phase transition as a function of U/t

First order metamagnetic phase transition

Abstract

The Heisenberg antiferromagnet, which arises from the large $U$ Hubbard model, is investigated on the $C_{60}$ molecule and other fullerenes. The connectivity of $C_{60}$ leads to an exotic classical ground state with nontrivial topology. We argue that there is no phase transition in the Hubbard model as a function of $U/t$, and thus the large $U$ solution is relevant for the physical case of intermediate coupling. The system undergoes a first order metamagnetic phase transition. We also consider the S=1/2 case using perturbation theory. Experimental tests are suggested.