Structure and stability of Mott-insulator shells of bosons trapped in an optical lattice

TL;DR

This paper explores creating and detecting shell-structured Mott-insulating phases of bosons in optical lattices, analyzing their stability and proposing an experimental method to spatially resolve these states for quantum information applications.

Contribution

It provides a simple recipe for creating multiple Mott-insulating shells and proposes an experimental technique to observe their spatial structure.

Findings

Shell structures can be created with any desired number of Mott-insulating layers.

The stability of these structures depends on experimental parameters.

Proposed magnetic field sweep method can detect the Mott configuration.

Abstract

We consider the feasibility of creating a phase of neutral bosonic atoms in which multiple Mott-insulating states coexist in a shell structure and propose an experiment to spatially resolve such a structure. This spatially-inhomogeneous phase of bosons, arising from the interplay between the confining potential and the short-ranged repulsion, has been previously predicted. While the Mott-insulator phase has been observed in an atomic gas, the spatial structure of this phase in the presence of an inhomogeneous potential has not yet been directly probed. In this paper, we give a simple recipe for creating a structure with any desired number of shells, and explore the stability of the structure under typical experimental conditions. The stability analysis gives some constraints on how successfully these states can be employed for quantum information experiments. The experimental probe we propose for observing this phase exploits transitions between two species of bosons, induced by applying a frequency-swept, oscillatory magnetic field. We present the expected experimental signatures of this probe, and show that they reflect the underlying Mott configuration for large lattice potential depth.