Thermal-conductivity measurements of gapless behavior produced by the proximity effect

The thermal conductivities Ks and Kn in the superconducting and normal states have been measured for six In-Bi films of varying thickness with Mn layers on each side. The graphs of KsKn against T show the characteristic linear variation of gapless systems near the transition temperature. In contrast to the expected behavior, KsKn approaches a finite value at low temperatures. This is interpreted in terms of localized states near the n-s boundary which cause gapless behavior at all temperatures.