Dynamically encircling an exceptional point by microwave fields in synthetic antiferromagnets

The impact of dynamically encircling an exceptional point (EP) on the low-energy spin excitations in antiparity-time (anti-PT) symmetric synthetic antiferromagnets is investigated by adopting the quantum adiabatic theorem and numerical simulations. Under adiabatic conditions, the dynamic evolution of the encircling EPs is found to converge toward a low-dissipation state. When the evolution begins from a phase with broken anti-PT symmetry, the chiral mode switching occurs. On the other hand, a phase with preserved anti-PT symmetry evolves during the encircling EPs through different magnon states into the same low-dissipation final state. Despite adhering to the adiabatic conditions for evolution parameters, nonadiabatic transitions are still observed in the antiferromagnetic system and can be effectively described by changes in the dynamical and topological aspects of the final magnon state. The results, as validated using full-edged numerical micromagnetic simulations, demonstrate the ability to explore non-Hermitian state transfer in flexible magnetic systems.