Time-Resolved Observation and Control of Superexchange Interactions with Ultracold Atoms in Optical Lattices

TLDR

Quantum mechanical superexchange interactions form the basis of quantum magnetism in strongly correlated electronic media. The study directly measures superexchange interactions using ultracold atoms in optical lattices. The authors measure superexchange by preparing spin mixtures in optical lattices, dynamically tuning the potential bias between neighboring sites to control interaction magnitude and sign, and compare the results to a two‑site Bose‑Hubbard model, finding good agreement and revealing corrections due to direct nearest‑neighbor interactions. They observe coherent superexchange‑mediated spin dynamics with coupling energies ranging from 5 Hz to 1 kHz, and the experimental data agree well with the Bose‑Hubbard model while highlighting corrections from direct nearest‑neighbor interactions.

Abstract

Quantum mechanical superexchange interactions form the basis of quantum magnetism in strongly correlated electronic media. We report on the direct measurement of superexchange interactions with ultracold atoms in optical lattices. After preparing a spin-mixture of ultracold atoms in an antiferromagnetically ordered state, we measure a coherent superexchange-mediated spin dynamics with coupling energies from 5 Hz up to 1 kHz. By dynamically modifying the potential bias between neighboring lattice sites, the magnitude and sign of the superexchange interaction can be controlled, thus allowing the system to be switched between antiferromagnetic or ferromagnetic spin interactions. We compare our findings to predictions of a two-site Bose-Hubbard model and find very good agreement, but are also able to identify corrections which can be explained by the inclusion of direct nearest-neighbor interactions.