Electromagnetically Induced Transparency of Interacting Rydberg Atoms with Two-Body dephasing

We study electromagnetically induced transparency of a ladder type configuration in ultracold atomic gases, where the upper level is an electronically highly excited Rydberg state. The strong two-body interaction in the Rydberg state leads to the excitation blockade, where all but one atoms are shifted out of resonance such that the transmission of the probe light is affected. We show that molecular coupling in the Rydberg state causes an effective, two-body dephasing. The presence of the two-body dephasing leads to a similar blockade effect. Hence the overall blockade effect is enhanced by the two-body dephasing. Through numerical and approximately analytical calculations, we find that the transmission is reduced drastically by the presence of two-body dephasing in the transparent window, which is accompanied by strong photon-photon anti-bunching. Around the Autler-Townes splitting, the photon bunching is amplified by the two-body dephasing.