Optical signature of subgap absorption in the superconducting state ofBa(Fe1−xCox)2As2 Academic Article uri icon

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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.

authors

  • Lobo, RPSM
  • Dai, YM
  • Nagel, U
  • Rõõm, T
  • Carbotte, JP
  • Timusk, Thomas
  • Forget, A
  • Colson, D

publication date

  • September 29, 2010