Self-consistent Single-band Approximation for Interacting Boson Systems

TL;DR

This paper introduces a self-consistent approach to the single-band approximation in interacting boson systems, accounting for interaction effects on Wannier functions, leading to nonlinear equations that improve modeling accuracy.

Contribution

It develops a self-consistent method for the single-band approximation, incorporating interaction effects into Wannier functions, which was previously neglected.

Findings

Self-consistent equations for Wannier functions derived

Simplified equations for superfluid and Mott insulator regimes

Illustrated with a double-well potential example

Abstract

Traditionally, the single-band approximation for interacting many-body systems is done with pre-determined single-particle Wannier functions, ignoring the dependence of the Wannier function on interaction. We show that the single-band approximation has to be done self-consistently to properly account the interaction effect on the Wannier functions. This self-consistent single-band approximation leads to a nonlinear equation for Wannier functions, which can be recast into a set of nonlinear equations for Bloch functions. These equations are simplified for two special cases, the superfluid regime and deep in the Mott insulator regime. A simple example with double-well potential is used to illustrate our results.