Variational Monte Carlo Study of Electron Differentiation around Mott Transition

TL;DR

This study uses an improved variational Monte Carlo method to analyze the Mott transition in the 2D Hubbard model, revealing electron differentiation and unconventional metallic states near the transition.

Contribution

It introduces an enhanced variational wave function with quantum-number projection and multi-variable optimization for accurate Mott transition analysis.

Findings

Identification of electron pockets and arc structures in momentum space.

Observation of nearly constant double occupancy near the transition.

First-order Mott transition driven by collapse of electron pockets and arcs.

Abstract

We study ground-state properties of the two-dimensional Hubbard model at half filling by improving variational Monte Carlo method and by implementing quantum-number projection and multi-variable optimization. The improved variational wave function enables a highly accurate description of the Mott transition and strong fluctuations in metals. We clarify how anomalous metals appear near the first-order Mott transition. The double occupancy stays nearly constant as a function of the on-site Coulomb interaction in the metallic phase near the Mott transition in agreement with the previous unbiased results. This unconventional metal at half filling is stabilized by a formation of ``electron-like pockets'' coexisting with an arc structure, which leads to a prominent differentiation of electrons in momentum space. An abrupt collapse of the ``pocket'' and ``arc'' drives the first-order Mott transition.