Fixed-node DMC for Fermions on a lattice: Application to the doped Fullerides

TL;DR

This paper develops a Monte Carlo approach using fixed-node diffusion techniques to study electron correlations and phase transitions in doped Fullerides modeled on a lattice.

Contribution

It introduces a model Hamiltonian for correlated electron hopping in Fullerides and applies optimized Monte Carlo methods to analyze their metal-insulator transition.

Findings

Effective Hamiltonian for doped Fullerides

Optimized Gutzwiller wavefunctions improve Monte Carlo results

Identification of the metal-insulator transition in doped Fullerides

Abstract

Fullerides are crystals made from C60 molecules. When doped with alkali metals the valence electrons of the alkali atoms are transfered to the C60 molecules. We show how to set up a model Hamiltonian to describe the correlated hopping of these electrons between C60 molecules. Then we discuss Monte Carlo methods for such lattice Hamiltonians, putting special emphasis on the optimization of Gutzwiller wavefunctions both in variational and fixed-node diffusion Monte Carlo. As application of these methods we analyze the metal-insulator transition in the integer-doped Fullerides.