Erratum: Observation of anisotropic diamagnetism above the superconducting transition in iron pnictide Ba1−xKxFe

Three-Dimensional Anisotropic Fluctuation Diamagnetism Around the Superconducting Transition of Ba1−x K x Fe2As2 Single Crystals in the Finite-Field (or Prange) Regime

“…Such a background contribution was determined by fitting a Curie-like function, m B (T) = a + bT + c/T, to the raw data in the temperature interval between 37 and 50 K (a, b, and c are free parameters). The lower bound corresponds to a temperature above which the fluctuation induced magnetic moment is estimated to be smaller than the experimental uncertainty [4]. The resulting fluctuation magnetic susceptibility ∆M/H=(m−m B )/VH is presented in Fig.…”

“…The Ba 1-x K x Fe 2 As 2 single crystal used in this work is the same as in Ref. 4. Details of its growth and characterization may be found in Ref.…”

“…This effect, also called precursor diamagnetism, is a very useful tool to probe the nature of a superconducting transition and to obtain material parameters as the upper critical fields or the anisotropy factor. [3] In the case of iron-pnictides, the only work on the subject was the above mentioned one [4], performed in a Ba 1-x K x Fe 2 As 2 single crystal (x=0.28) with magnetic fields applied both parallel and perpendicular to the ab (Fe) layers. It was shown that the three-dimensional anisotropic Ginzburg-Landau approach (3D-aGL) with a total-energy cutoff (Ref.…”

Comment on “Multiorbital Effects on the Transport and the Superconducting Fluctuations in LiFeAs”

“…These authors conclude that the conductivity induced by fluctuations, ∆σ, follows a two-dimensional (2D) behavior even close to T c , in spite that for LiFeAs the transverse coherence length ξ c (0) ≈ 1.6 nm is larger than the Fe-layers spacing (s = 0.636 nm), which would rather suggest a threedimensional (3D) behavior. This proposal would have implications in the understanding of the multiband structure of iron pnictides, but it also contrasts with the 3D behavior observed near T c in the same compound [2] and in other iron pnictides with even smaller ξ c (0)/s [3]. Here we show that the proposal of Ref.[1] could be an artifact associated to an inadequate subtraction of the normalstate (or background ) conductivity, σ B .Note first that in the clean crystals studied in Ref.[1] σ B is orders of magnitude larger than the expected fluctuation contribution: at a reduced temperature ε ≡ ln(T /T c ) = 10 −1 the Aslamazov-Larkin (AL) approach predicts ∆σ 2D ∼ 2.5 × 10 5 Ω −1 m −1 and ∆σ 3D…”

Shrinking of the fluctuation region in a two-band superconductor

“…Usually, the width of the critical domain is being investigated in various high-T c materials only under applied magnetic fields [48][49][50][51][52]. Next we discuss the qualitative behaviour of Gi d as a function of the critical temperature in two-band model.…”