Excitation spectrum of Mott shells in optical lattices

TL;DR

This paper presents a theoretical study of the excitation spectrum in Mott-insulating optical lattices, introducing a fast numerical method to analyze large systems and exploring the properties of Mott shells and their interfaces.

Contribution

It introduces a new numerical approach for calculating excitation spectra and ground states in large optical lattice systems, accounting for multi-band effects and tunnelling perturbatively.

Findings

Good agreement with exact diagonalization for small systems

Identification of gapless excitations at Mott shell interfaces

Characterization of spectral properties of Mott shells

Abstract

We theoretically study the excitation spectrum of confined macroscopic optical lattices in the Mott-insulating limit. For large systems, a fast numerical method is proposed to calculate the ground state filling and excitation energies. We introduce many-particle on-site energies capturing multi-band effects and discuss tunnelling on a perturbative level using an effectively restricted Hilbert space. Results for small one-dimensional lattices obtained by this method are in good agreement with the exact multi-band diagonalization of the Hamiltonian. Spectral properties associated with the formation of regions with constant filling, so-called Mott shells, are investigated and interfaces between the shells with strong particle fluctuations are characterized by gapless local excitations.