Formation of spatial shell structures in the superfluid to Mott insulator transition

TL;DR

This paper reports the direct observation of the superfluid to Mott insulator transition in a Bosonic quantum gas, revealing the formation of spatial shell structures consistent with theoretical predictions.

Contribution

It introduces a novel experimental technique to spatially resolve local filling factors during the phase transition in an optical lattice.

Findings

Observation of shell structures during the transition

Agreement between experimental data and theoretical models

Demonstration of local spin state modification

Abstract

We report on the direct observation of the transition from a compressible superfluid to an incompressible Mott insulator by recording the in-trap density distribution of a Bosonic quantum gas in an optical lattice. Using spatially selective microwave transitions and spin changing collisions, we are able to locally modify the spin state of the trapped quantum gas and record the spatial distribution of lattice sites with different filling factors. As the system evolves from a superfluid to a Mott insulator, we observe the formation of a distinct shell structure, in good agreement with theory.