Abstract
Far-infrared reflectance of a film has been measured by Fourier-transform spectroscopy for frequencies above and below the superconducting transition. The data provide clear experimental evidence for the onset of a superconducting gap at at On increasing the temperature the gap energy increases, contrary to what is expected in isotropic BCS superconductors. The small zero-temperature gap value and its unconventional increases on increasing temperature can only be explained by a highly anisotropic or multiple gap function.
- Received 9 January 2002
DOI:https://doi.org/10.1103/PhysRevB.65.172502
©2002 American Physical Society