Development of 2e-ARPES to Measure Correlated Electron Pairs in Unconventional Superconductors

Probing pairing symmetries and intertwined orders in strongly correlated systems constitute some of the main challenges in modern condensed matter physics. Here we present our group's recent progress in the development of two electron coincidence photoemission spectroscopy (2e-ARPES) as a platform to probe finite-momentum pairing states in superconductors, such as the pair center-of-mass momentum as well as the spin state of Cooper pairs. We present our experimental realization of 2e-ARPES by means of two time-of flight photoelectron analyzers and a high harmonic generation (HHG) tabletop source of XUV photons as a probe. We use a hardware timing circuit and a post-processing algorithm to distinguish between accidental and true coincident detection events. We will also share some preliminary 2e-ARPES data in Bi-2212.