Ultrafast Melting of Superconductivity in an Fe-Based Superconductor

Optically pumping systems out of equilibrium provides a unique interpretation of quantum states of matter due to their ability to disentangle certain degrees of freedom, often yielding information inaccessible from equilibrium measurements. Here, we employ time-and-angle resolved photoemission spectroscopy (trARPES) on an iron-based superconductor to directly observe the destruction of superconducting order on ultrafast timescales. Close examination of these ultrafast changes provides vital clues to the pairing strength as debated in the BCS-BEC crossover. Our results expose the wealth of information that can be learned from probing the nonequilibrium changes to the band structure in the iron-based superconductors.