Doublon-Holon Binding Effects on Mott Transitions in Two-Dimensional Bose Hubbard Model

TL;DR

This paper investigates the Mott transition in a two-dimensional Bose Hubbard model using a variational Monte Carlo approach, emphasizing doublon-holon binding effects that differ from traditional Brinkman-Rice transitions.

Contribution

It introduces a four-body doublon-holon correlation factor into the variational wave function, improving energy estimates and capturing the superfluid-insulator transition more accurately.

Findings

Doublon-holon binding is crucial for describing the Mott transition.

The new variational wave function better captures the transition characteristics.

Transition features differ from Brinkman-Rice-type transitions.

Abstract

A mechanism of Mott transitions in a Bose Hubbard model on a square lattice is studied, using a variational Monte Carlo method. Besides an onsite correlation factor, we introduce a four-body doublon-holon factor into the trial state, which considerably improves the variational energy and can appropriately describe a superfluid-insulator transition. Its essense consists in binding (and unbinding) of a doublon to a holon in a finite short range, identical with the cases of fermions. The features of this transition are qualitatively different from those of Brinkman-Rice-type transitions.