Frequency-detuned exceptional surface assisted by the self-coherence effect of a giant atom

Exceptional points (EPs), singularities in non-Hermitian systems where eigenvalues and eigenvectors coalesce, have enabled groundbreaking phenomena such as unidirectional invisibility, chiral transmission, and enhanced sensing. However, their sensitivity to perturbations, particularly frequency detuning, poses a significant challenge in realizing robust EPs. While exceptional surfaces (ESs) have been proposed to mitigate this issue, frequency consistency remains a critical requirement for achieving EPs in real-coupling systems. Here, we address this limitation by introducing a giant atom-based system, leveraging the unique self-coherent coupling effects of giant atoms to construct frequency-detuned EPs and ESs in real-coupling systems. Using a split-ring resonator coupled to a meandering microwave transmission line, we experimentally demonstrate an ES in a frequency-detuned regime. The giant atom's multi-point non-local coupling enables precise control over frequency detuning and linewidth, offering a new degree of freedom for engineering non-Hermitian degeneracies. Our results not only expand the scope of ESs but also highlight the potential of giant atoms in exploring novel non-Hermitian photonics, including synthetic dimensions, chirality reversal, and stable EP-enhanced sensors.