Theory of fluctuation conductivity from interband pairing in pnictide superconductors

We derive the effective action for superconducting fluctuations in a four-band model for pnictides, discussing the emergence of a single critical mode out of a dominant interband pairing mechanism. We then apply our model to calculate the paraconductivity in two-dimensional and layered three-dimensional systems and compare our results with recent resistivity measurements in ${\text{SmFeAsO}}_{0.8}{\text{F}}_{0.2}$.

Figure 1

(Color online) Comparison between the experimental paraconductivity for a ${\text{SmFeAsO}}_{0.8}{\text{F}}_{0.2}$ sample studied in Ref. 4 (blue circles) and the 2D (dashed line) and 3D (solid line) expressions of the AL paraconductivity [Eqs. (8, 9)]. For the 3D paraconductivity a coherence length ${\xi }_z=19\text{Å}$ has been used while for the 2D case the structural distance between layers $d=8.4\text{Å}$ has been inserted.