Dynamical Evolution of an Effective Two-Level System with \mathcalPT Symmetry

We investigate the dynamics of parity- and time-reversal (\mathcalPT) symmetric two-energy-level atoms in the presence of two optical and one radio-frequency fields. The strength and relative phase of fields can drive the system from the unbroken to the broken \mathcalPT symmetric regions. Compared with the Hermitian model, Rabi-type oscillation is still observed, and the oscillation characteristics are also adjusted by the strength and relative phase in the region of the unbroken \mathcalPT symmetry. At the exception point, the oscillation breaks down. To better understand the underlying properties we study the effective Bloch dynamics and find that the emergence of the z components of the fixed points is the feature of the \mathcalPT symmetry breaking and the projections in the x–y plane can be controlled with high flexibility compared with the standard two-level system with the \mathcalPT symmetry. It helps to study the dynamic behavior of the complex \mathcalPT symmetric model.