Resonance-enhanced collective effect in a triangle arrangement of Rydberg atoms with anisotropic interactions

We investigate the collective excitation effect in a scheme where three identical Rydberg atoms are arranged in an equilateral triangular lattice. By using a static electric field polarizing the atomic dipoles, the dipole-dipole interactions between two Rydberg atoms are essentially anisotropic and can even disappear in several special resonance cases. For that fact, we observe the collectively enhanced excitation probability of a single Rydberg atom in resonant areas in the case of strong blockade, and that of double or triple Rydberg atoms in the case of partial blockade. To give more evidence for this collective excitation enhancement, we study the two-body quantum correlation between three Rydberg atoms, as well as the dependence of the blockade radius on the length of triangle sides, which present a good agreement with the excitation properties.