Symmetrized PQMC Studies of the ground state of $C_{60}$

TL;DR

This paper introduces a symmetrized Projector Quantum Monte Carlo method to accurately study the ground state and structural distortions of a $C_{60}$ molecule within the Hubbard model, emphasizing symmetry preservation.

Contribution

The paper develops a new symmetrized QMC approach that maintains system symmetries and applies it to analyze electron correlations and distortions in $C_{60}$.

Findings

Largest amplitude for $H_{g}$ distortion.

Significant spin correlations in $T_{2g}$ and $G_{u}$ representations.

Enhanced accuracy in correlation function estimates.

Abstract

We develop a new $\it {symmetrized}$ version of the Projector Quantum Monte Carlo (SPQMC) method which preserves the symmetries of the system by simultaneously sampling all symmetry related Ising configurations at each MC step and use it to study the effect of electron correlations on a single $C_{60}$ molecule and its structural motifs, within the Hubbard model. The SPQMC method allows more accurate estimates of correlation functions as seen from calculations on small systems. We study the ground state properties of a single fullerene molecule, with and without bond alternation. We construct projections of the bond orders and spin-spin correlation functions on the space of irreducible representations of the icosahedral point group. These projections, analogous to the structure factors of translationally invariant systems, give the amplitudes for distortions which transform as the irreducible representations of the point group. The amplitude for the $H_{g}$ distortion is the largest while the spin structure has large weights in the $T_{2g}$ and $G_{u}$ representations.