Observation of interaction-induced gauge fields in a Bose-Einstein condensate based on micromotion control in a shaken two-dimensional lattice

We demonstrate an interaction-induced gauge field for Bose-Einstein condensates in a modulated two-dimensional optical lattice. The gauge field results from the synchronous coupling between the interactions and micromotion of the atoms. As a first step, we show that a coherent shaking of the lattice in two directions can couple the momentum and interactions of atoms and break the four-fold symmetry of the lattice. We then create a full interaction-induced gauge field by modulating the interaction strength in synchrony with the lattice shaking. When a condensate is loaded into this shaken lattice, the gauge field acts to preferentially prepare the system in different quasimomentum ground states depending on the modulation phase. We envision that these interaction-induced fields, created by fine control of micromotion, will provide a stepping stone to model new quantum phenomena within and beyond condensed matter physics.