Detecting Self-Orthogonality at Exceptional Points through Diverging Rabi Oscillations in PT-Symmetric Systems

Non-Hermitian systems have attracted significant attention in recent years due to their ability to describe setups that are not fully isolated from their environment. A key feature of such systems is the presence Exceptional Points (EPs) which are parameter space singularities where eigenstates coalesce, Parity-Time (PT) symmetry breaks, and the surrounding eigenvalue surface exhibits exotic topology. These intriguing properties offer potential for applications such as enhanced sensing and mode splitting. However, detecting the coalescence of states, often referred to as self-orthogonality, remains challenging. In this talk, I will demonstrate how Rabi oscillations can be used to observe the direct effects of the self-orthogonality. Based on a periodically driven PT-symmetric model, I will show that the Rabi frequency diverges at the EP due to the coalescence of eigenstates and discuss how this divergence could be observed — such as in topolectric circuits or optical systems— by measuring a real space global observable.