Coalescence of nonreciprocal exceptional points in magnetized PT -symmetric systems

We study the Lorentz nonreciprocal transmission and nonreciprocal complex band structures supported in a $\mathcal{P}\mathcal{T}$-symmetric waveguide sandwiched by magnetized layers. We found that, near the emergency and coalescence of exceptional points, nonreciprocal transmission can be significantly enhanced by the non-Hermitian properties. With the help of gain-loss balance, one-way light transmission could be achieved even in the presence of a weak magnetic field. The results may offer us insight into the interplay between Lorentz nonreciprocity and non-Hermiticity.