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arXiv · 1007.3761

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·T. Room·J. P. Carbotte·T. Timusk·A. Forget·D. Colson
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Abstract

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 low frequency response. This task is achieved by introducing an extra Drude peak in the superconducting state representing sub-gap absorption, other than thermally broken pairs. This extra peak and the coexisting $s$-wave response respect the total sum rule indicating a common origin for the carriers. We discuss the possible origins for this absorption as (i) quasiparticles due to pair-breaking from interband impurity scattering in a two band $s_{\pm}$ gap symmetry model, which includes (ii) the possible existence of impurity levels within an isotropic gap model; or (iii) an indication that one of the bands is highly anisotropic.

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R. P. S. M. Lobo, Y. M. Dai, U. Nagel, T. Room, J. P. Carbotte, T. Timusk, A. Forget, D. Colson. 2010-07-21. Optical signature of sub-gap absorption in the superconducting state of Ba(Fe,Co)2As2. https://doi.org/10.1103/physrevb.82.100506

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