Signatures of spatial inversion asymmetry of an optical lattice observed in matter-wave diffraction

TL;DR

This paper investigates how small inversion asymmetries in a honeycomb optical lattice affect matter-wave diffraction patterns, revealing significant asymmetries even with minimal potential imbalance, and explains these effects through scattering and band structure analysis.

Contribution

It demonstrates that minor inversion asymmetries in optical lattices cause observable diffraction asymmetries, providing a quantitative understanding through theoretical modeling.

Findings

Small potential asymmetry causes pronounced diffraction asymmetry.

Asymmetry explained by Kapitza-Dirac scattering and band structure analysis.

Results inform coherent atom optics and interpretation of time-of-flight measurements.

Abstract

The structure of a two-dimensional honeycomb optical lattice potential with small inversion asymmetry is characterized using coherent diffraction of $^{87}$Rb atoms. We demonstrate that even a small potential asymmetry, with peak-to-peak amplitude of $\leq 2.3\%$ of the overall lattice potential, can lead to pronounced inversion asymmetry in the momentum-space diffraction pattern. The observed asymmetry is explained quantitatively by considering both Kapitza-Dirac scattering in the Raman-Nath regime, and also either perturbative or full-numerical treatment of the band structure of a periodic potential with a weak inversion-symmetry-breaking term. Our results have relevance for both the experimental development of coherent atom optics and the proper interpretation of time-of-flight assays of atomic materials in optical lattices.