Two-Body Kapitza-Dirac Scattering of One-Dimensional Ultracold Atoms

TL;DR

This paper develops an exact two-body model for Kapitza-Dirac scattering of ultracold atoms in one dimension, revealing how interactions influence diffraction patterns and identifying regimes where common approximations break down.

Contribution

It introduces a numerically exact two-body approach to analyze strongly interacting ultracold atoms under Kapitza-Dirac scattering, providing detailed insights into interaction effects.

Findings

Interaction strength significantly alters diffraction patterns.

Impulsive approximation accuracy depends on interaction regime.

Strong attraction and small wavenumber regimes challenge common models.

Abstract

Kapitza-Dirac scattering, the diffraction of matter waves from a standing light field, is widely utilized in ultracold gases, but its behavior in the strongly interacting regime is an open question. Here we develop a numerically-exact two-body description of Kapitza-Dirac scattering for two contact-interacting atoms in a one-dimensional harmonic trap subjected to a pulsed optical lattice, enabling us to obtain the numerically exact dynamics. We map how interaction strength, lattice depth, lattice wavenumber, and pulse duration reshape the diffraction pattern, leading to an interaction-dependent population redistribution in real and momentum-space. By comparing the exact dynamics to an impulsive sudden-approximation description, we delineate the parameter regimes where it remains accurate and those, notably at strong attraction and small lattice wavenumber, where it fails. Our results provide a controlled few-body benchmark for interacting Kapitza-Dirac scattering and quantitative guidance for Kapitza-Dirac-based probes of ultracold atomic systems.