We have developed a new variant of angle-resolved photoemission spectroscopy (ARPES) that gives greatly improved accuracy of gap measurements compared to all other spectroscopic probes and also allows us to make the first quantitative extraction of the pair-breaking scattering rates. The results from this new method give critical new insights into the origin of pseudogaps, Fermi arcs, and superconductive pairing in the cuprate superconductors, helping us answer the critical question “What sets the T _c ?”

Following this I will present recent results from some iridium oxides, which mix strong spin orbit coupling with correlation (Mott) effects. When doped with carriers, many of the iconic properties of the cuprates such as Fermi arcs and pseudogaps can also be found in these compounds, indicating that these materials should become a fertile playground for the study of correlated electron matter.