Anisotropic deformation of the Rydberg-blockade sphere in few-atom systems

A Rydberg-blockade sphere provides an intriguing picture by which a number of collective many-body effects caused by the strong Rydberg-Rydberg interactions can be clearly understood and profoundly investigated. In the present work, we develop a definition for the effective two-atom blockade radius and show that the original spherically shaped blockade surface would be deformed when the real number of atoms increases from two to three. This deformation of the blockade sphere reveals spatially anisotropic and shrunken properties which strongly depend on the interatomic distance. In addition, we also study the optimal conditions for the Rydberg antiblockade effect and make predictions for improving the antiblockade efficiency in few-atom systems.