Imaging the Three-Dimensional Fermi-Surface Pairing near the Hidden-Order Transition in URu2Si2 Using Angle-Resolved Photoemission Spectroscopy

We report angle-resolved photoemission spectroscopy experiments probing deep into the hidden-order state of URu2Si2, utilizing tunable photon energies with sufficient energy and momentum resolution to detect the near Fermi-surface (FS) behavior. Our results reveal (i) the full itinerancy of the 5f electrons, (ii) the crucial three-dimensional k-space nature of the FS and its critical nesting vectors, in good comparison with density-functional theory calculations, and (iii) the existence of hot-spot lines and pairing of states at the FS, leading to FS gapping in the hidden-order phase.