Hannover 2016 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 58: Poster: Quantum Optics and Photonics IV

Q 58.32: Poster

Thursday, March 3, 2016, 16:30–19:00, Empore Lichthof

Symmetry transtion in a periodic parity-time-symmetric potential induced in an atomic sytem — •Lida Zhang and Jörg Evers — Max Planck Institute for Nuclear Physics, 69117 Heidelberg

We propose a feasible scheme to produce a periodic parity-time (PT) symmetric potential using standing-wave laser fields in an atomic system which combines two different physical processes, i.e., electromagnetically induced transparency and active Raman gain. The resulting band structure of the system shows completely real eigenvalues when the imaginary part of the potential is below a certain limit, corresponding an unbroken PT phase. However, as exceeding this limit, pairs of complex eigenvalues start to enter in the band edge, referring to a broken PT phase. The transition between unbroken and broken PT symmetry can be further characterized by an order parameter. Under two-level approximation, we obtain analytical expressions for the eigenvalues, with which we understand the emergence of complex eigenvalues in a deeper physical level. Moreover, we find a simple analytical solution for the order parameter, which agrees perfectly well with numerical results. Finally, additional nonlocal nonlinear effects is addressed by introducing Rydberg-Rydberg interactions. We find the symmetry transition can be either broken or recovered by the nonlocal nonlinear effects.