Coexistence of exceptional ring and exceptional surface in a doped molecular chain*

In recent years, the spectral features and topological properties associated with coalescing eigenstates at exceptional points have been studied in a wide range of physical contexts. In this work, we reveal the occurrence of higher-dimensional exceptional manifolds in the spectrum of a magnetized donor atom at the endpoint of a molecular chain. We demonstrate the presence of both an exceptional ring and an exceptional surface in the parameter space of an externally applied magnetic field, which reflect underlying symmetries in the model. We propose electron spin resonance (ESR) as a method to observe these exceptional manifolds in experiment. We emphasize that the exceptional manifolds arise in our system due to the influence of the microscopic degrees of freedom ascribed to the molecular chain. This is as opposed to treatments in which explicit non-Hermitian elements are introduced to represent macroscopic approximations over such degrees of freedom.