Two-electron photoemission spectroscopy in Topological Superconductors

We demonstrate that the photo-electron counting rate, $P^{(2)}$, measured in two electron coincidence spectroscopy (2$e$-ARPES) experiments, provides unprecedented insight into the nature of topological superconductivity. In particular, we show that the spin dependence of $P^{(2)}$ allows one to detect superconducting spin-triplet correlations that are induced in a topological superconductor even in the absence of an associated triplet superconducting order parameter. This ability to detect spin-triplet correlations allows one to distinguish between two recently proposed scenarios for the microscopic origin of topological superconductivity in FeSe$_{0.45}$Te$_{0.55}$. Finally, we show that $P^{(2)}$ exhibits a characteristic intensity maximum that can be employed to detect topological phase transitions.