Spin vortices in Janus colloid monolayer

Colloid has been used for decades to imitate various aspects of molecular materials and has provided a foundation for confirming theoretical models of nucleation or melting. Here, we propose an experimental system where Janus spheres are on top of a triangular lattice, and interaction between them is orientationally dependent. In this model, we control orientational interaction between Janus spheres by tuning the applied electric field. By this model, we find a vortex pattern on Janus colloidal monolayer and validate that the z-component of Janus spheres' orientation is correlated with their movement in XY-plane. Our works will probably provide us with insights into correlations between orientational collective motions and topological defects.