Rydberg blockade in an ultracold strontium gas revealed by two-photon excitation dynamics

Abstract

We demonstrate the interaction-induced blockade effect in an ultracold 88 Sr gas via studying the time dynamics of a two-photon excitation to the triplet Rydberg series 5sns 3 S1 for five different principle quantum numbers n ranging from 19 to 37. By using a multi-pulse excitation sequence to increase the detection sensitivity we could identify Rydberg-excitation-induced atom losses as low as < 1%. Based on an optical Bloch equation formalism, treating the Rydberg-Rydberg interaction on a mean-field level, the van der Waals coefficients are extracted from the observed dynamics, which agree fairly well with ab initio calculations.