Anomalous excitation enhancement with Rydberg-dressed atoms

We develop the research achievement of recent work [Gärttner, Phys. Rev. Lett. 113, 233002 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.233002], in which an anomalous excitation enhancement is observed in a three-level Rydberg-atom ensemble with many-body coherence. In our theoretical analysis, this effect is ascribed to the existence of a quasidark state as well as its avoided crossings to nearby Rydberg-dressed states. Moreover, we show that with an appropriate control of the optical detuning to the intermediate state, the enhancement can evoke a direct facilitation to atom-light coupling that even breaks through the conventional N limit of strong-blockaded ensembles. As a consequence, the intensity of the probe laser for intermediate transition can be reduced considerably, increasing the feasibility of experiments with Rydberg-dressed atoms.