Strong magnetic interaction between dysprosium atoms at subwavelength distances

Dysprosium atoms, which are among the most magnetic atoms in the periodic table, feature magnetic dipolar interactions that are a hundred times stronger than those of alkali atoms. However, this interaction remains weak compared to other energy scales in the system, such as contact interactions or the temperature. Therefore, to study many-body physics that arises from magnetic interactions, it is crucial to develop protocols to place atoms much closer than conventional methods allow. 

Here we take a first step toward this goal by characterizing the magnetic interaction between two dysprosium atoms confined in a tightly trapped harmonic potential. By confining atom pairs to 20 nm length scale in a deep optical lattice, we showed that the magnetic interaction strength can be as large as 10 kHz, which can be measured in time-of-flight. We also discuss a route to confining atom pairs in a double-well potential with ~50 nm separation, which would further enhance dipolar interactions and open a new regime for dipolar many-body physics.