Probing an Ultracold-Atom Crystal with Matter Waves

TL;DR

This paper demonstrates that Bragg diffraction of neutral atoms can effectively characterize spatial and spin orderings in ultracold atomic gases within optical lattices, offering a non-destructive probing method for strongly correlated phases.

Contribution

The authors experimentally show that matter wave diffraction can reveal spatial and spin ordering in optical lattice systems, expanding tools for studying quantum gases.

Findings

Bragg diffraction infers spatial ordering and localization of atoms.

Increased lattice depth suppresses inelastic scattering.

Atomic de Broglie waves detect antiferromagnetic ordering.

Abstract

Atomic quantum gases in optical lattices serve as a versatile testbed for important concepts of modern condensed-matter physics. The availability of methods to characterize strongly correlated phases is crucial for the study of these systems. Diffraction techniques to reveal long-range spatial structure, which may complement \emph{in situ} detection methods, have been largely unexplored. Here we experimentally demonstrate that Bragg diffraction of neutral atoms can be used for this purpose. Using a one-dimensional Bose gas as a source of matter waves, we are able to infer the spatial ordering and on-site localization of atoms confined to an optical lattice. We also study the suppression of inelastic scattering between incident matter waves and the lattice-trapped atoms, occurring for increased lattice depth. Furthermore, we use atomic de Broglie waves to detect forced antiferromagnetic ordering in an atomic spin mixture, demonstrating the suitability of our method for the non-destructive detection of spin-ordered phases in strongly correlated atomic gases.