Two-electron photoemission spectroscopy in topological superconductors

We demonstrate that the photoelectron counting rate, $P^{\left(2\right)}$, measured in two-electron coincidence spectroscopy experiments, provides insight into the nature of topological superconductivity. In particular, we show that the spin dependence of $P^{\left(2\right)}$ 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 ${\mathrm{FeSe}}_{0.45}{\mathrm{Te}}_{0.55}$. Finally, we show that $P^{\left(2\right)}$ exhibits a characteristic intensity maximum that can be employed to detect topological phase transitions.