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

Elucidating the nature of electronic correlations, intertwined orders, and pairing symmetries in unconventional superconductors is one of the main challenges in modern condensed matter physics. Here we present our group's recent development of two electron coincidence photoemission spectroscopy (2e-ARPES) as a promising platform to probe the properties of finite-momentum pairing states in superconductors, such as the pair center-of-mass momentum as well as the spin state of Cooper pairs. We will specifically detail how we use high harmonic generation (HHG) in a nobel gas medium as a stable, high-flux tabletop source of XUV photons as a probe for 2e-ARPES. We will also discuss how the selection of specific photon energies from the HHG spectrum enables precise detection of correlated electron events from controllable locations in the material band structure.