Excitation spectrum and momentum distribution of the ionic Bose-Hubbard model

TL;DR

This paper analyzes the excitation spectrum and momentum distribution of the ionic Bose-Hubbard model across various phases, revealing characteristic gapped and gapless modes, and how these relate to observable momentum peaks.

Contribution

It provides a theoretical analysis of the excitation spectrum and momentum distribution in the ionic Bose-Hubbard model using the Green's function method across multiple phases.

Findings

Gapped and gapless modes identified in different phases.

Momentum distribution peaks at zone corners near phase boundaries.

Excitation spectrum explains features of momentum distribution.

Abstract

We investigate the excitation spectrum and momentum distribution of the ionic Bose-Hubbard model by the standard basis operator method. We derive Green's functions in the random phase approximation in Mott insulator, superfluid, charge density wave, and supersolid phases. The excitation spectrum has gapped modes and gapless Goldstone modes in the superfluid and supersolid phases. We show that the momentum distribution has a peak at the zone corner in the supersolid phase and the charge density wave phase close to the phase boundary. In addition, we demonstrate that the momentum distribution can be explained by the excitation spectrum and spectral weights of hole excitation modes.