Optical signature of sub-gap absorption in the superconducting state of Ba(Fe,Co)2As2

R. P. S. M. Lobo, Y. M. Dai, U. Nagel +5

The optical conductivity of Ba(Fe${}_{0.92}$Co${}_{0.08}$)${}_2$As${}_2$ shows a clear signature of the superconducting gap, but a simple $s$-wave description fails in accounting for the l…