Disordered Superconductivity in Fe(Te,Se)

The interplay of topology, superconductivity, and magnetism has made iron chalcogenide compounds an exciting playground for exploring exotic quantum states; however, the role of disorder has been largely neglected to date. Using time domain terahertz spectroscopy, we find anomalous low-energy absorption in the superconducting state of Fe(Te,Se) thin films and heterostructures. These features are accurately modeled according to theories of disordered superconductivity originally developed for cuprates and the superconductor-insulator transition. These results suggest that disorder plays an overlooked role in the behavior of Fe(Te,Se), which may have wide-ranging consequences for the interpretation of the various exotic phenomena observed in these exciting compounds.