Post-experiment coincidence detection techniques for direct detection of two-body correlations

It is one challenge to develop experimental techniques for direct detection of the many-body correlations of strongly correlated electrons, which exhibit a variety of unsolved mysteries. In this article, we present a $\mathit{\text{post-experiment}}$ coincidence counting method and propose two $\mathit{\text{post-experiment}}$ coincidence detection techniques, $\mathit{\text{post-experiment}}$ coincidence angle-resolved photoemission spectroscopy (cARPES) and $\mathit{\text{post-experiment}}$ coincidence inelastic neutron scattering (cINS). By coincidence detection of two photoelectric processes or two neutron-scattering processes, the $\mathit{\text{post-experiment}}$ coincidence detection techniques can detect directly the two-body correlations of strongly correlated electrons in particle-particle channel or two-spin channel. The $\mathit{\text{post-experiment}}$ coincidence detection techniques can be implemented upon the $\mathit{\text{pulse}}$-resolved angle-resolved photoemission spectroscopy (ARPES) or inelastic neutron scattering (INS) experimental apparatus with $\mathit{\text{pulse}}$ photon or neutron source. When implemented experimentally, they will be powerful techniques to study the highly esoteric high-temperature superconductivity and the highly coveted quantum spin liquids.