Identifying topologically critical band from pinch-point singularities in spectroscopy

In this paper, we investigate the relationship between pinch point singularities observed in energy- and momentum-resolved spectroscopy and topologically non-trivial gapless points. We show that these singularities are a universal signature, and that the Berry flux encoded must be $n\pi$ for an $n-$fold pinch point under suitable symmetry protection. Our results apply to most systems and are independent of their microscopic details. Hence they provide a new way to identify topological phases without requiring detailed knowledge of the microscopic model. Our work can be readily applied in spectroscopy experiments on various platforms.