Impurities in multiband superconductors

Korshunov, M. M.; Togushova, Yu.N.; Dolgov, O. V.

doi:10.3367/ufne.2016.07.037863

Cited by 38 publications

(44 citation statements)

References 182 publications

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“…To calculate the gaps and the critical temperature by the three-band Eliashberg equations [40][41][42] we solve six coupled equations for the frequency dependent gaps ∆ i (iω n ) and renormalization functions Z i (iω n ), where i is a band index ranging from 1 to 3 and ω n are the Matsubara frequencies. The imaginary-axis equations 40,43,44 read:…”

Section: Solving the Eliashberg Equationsmentioning

confidence: 99%

Comprehensive Eliashberg analysis of microwave conductivity and penetration depth of K-, Co-, and P-substituted BaFe2As2

et al. 2019

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We report on the combined experimental and theoretical analysis of microwave-frequency electromagnetic response of BaFe2As2 single crystals with different substitutions: K in the site of Ba (hole doping), Co in the Fe site (electron doping) and P in the As site (isovalent substitution). Measurements by a coplanar resonator technique lead to the experimental determination of the penetration depth and microwave conductivity as a function of temperature. The whole set of data is analyzed within a self-consistent three-band s±-wave Eliashberg approach, able to account for all the main observed features in the different properties. Beside the validation of the model itself, the comparison between experiment and theory allows discussing the possible role of the Fe-As planes in defining the superconducting properties of these compounds, the relevance of coherence effects, and the presence of nodes in the superconducting order parameter.

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Section: Solving the Eliashberg Equationsmentioning

confidence: 99%

Comprehensive Eliashberg analysis of microwave conductivity and penetration depth of K-, Co-, and P-substituted BaFe2As2

et al. 2019

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“…A change of sign as a consequence of increased disorder was discussed in refs 32–34 . To qualitatively understand this behavior in our case, it is sufficient to write the Eliashberg equation for the gap Δ 2 : = , where λ 23 , and Z 2 are positive, while Δ 2 is negative and δ mn is the Kronecker delta.…”

Section: Resultsmentioning

confidence: 99%

“…Within the Born approximation, the model is sensitive to the global effect of disorder rather than to the details of defects. As a matter of fact, a more general theory to study the role of defects in superconductors was developed 32–34 , but in the proposed formulation only applies to two-band systems, even if its generalization to more bands is possible. Since there is evidence that in the system under study the inter-band coupling is predominant and the number of bands to be considered is greater than or equal to three 35,36 , and since using two-band models would lead to the appearance of intra-band terms that do not have a physical interpretation 37 , we preferred to consider three conducting bands, rather than a more precise parametrization of disorder.…”

Section: Introductionmentioning

confidence: 99%

Effects of disorder induced by heavy-ion irradiation on (Ba1−x K x )Fe2As2 single crystals, within the three-band Eliashberg s± wave model

Ghigo

Ummarino

Gozzelino

et al. 2017

Sci Rep

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One of the open issues concerning iron-based superconductors is whether the s± wave model is able to account for the overall effects of impurity scattering, including the low rate of decrease of the critical temperature with the impurity concentration. Here we investigate Ba1−xKxFe2As2 crystals where disorder is introduced by Au-ion irradiation. Critical temperature, T c, and London penetration depth, λ L, were measured by a microwave resonator technique, for different values of the irradiation fluence. We compared experimental data with calculations made on the basis of the three-band Eliashberg equations, suitably accounting for the impurity scattering. We show that this approach is able to explain in a consistent way the effects of disorder both on T c and on λ L(T), within the s± wave model. In particular, a change of curvature in the low-temperature λ L(T) curves for the most irradiated crystals is fairly well reproduced.

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“…Since the FeSC discovery, several works on disentanglement of the sign-changing and sign-preserving order parameters with help of nonmagnetic impurities were published [17,34,63,[71][72][73][74].…”

Section: Identification Of the Symmetry Of The Order Parameter With Tmentioning

confidence: 99%

A multiband Eliashberg‐approach to iron‐based superconductors

Efremov

Drechsler

Rösner

et al. 2017

Physica Status Solidi (b)

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Since the discovery of the Fe-based superconductors (FeSC) a lot of efforts has been applied to elucidate the microscopic mechanism behind cooper pairing and the symmetry of the order parameter. Examination of effective interactions of electrons with spin-fluctuations in these systems yield that couplings are not weak and the materials have to be considered in a strong coupling scheme. In the present article, we review some aspects of the description of iron-based superconductors in the frame of the Eliashberg approach for multiband systems. The application of the Eliashberg scheme is demonstrated with two compounds Ba0.6K0.4Fe2As2 and Ca0.32Na0.68Fe2As2. In both cases, it was found that these materials are in the intermediate coupling regime. Further, we consider effects of impurities on physical properties of multiband superconductors. It is demonstrated that the impurities affect nontrivially the superconducting properties. In particular, they may trigger a symmetry change of superconducting order parameters. This effect can be used for determination of the superconducting order parameter. Finally, we consider KFe2As2 and show that its thermodynamic properties are consistent with a nodal superconducting order parameter

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Impurities in multiband superconductors

Cited by 38 publications

References 182 publications

Comprehensive Eliashberg analysis of microwave conductivity and penetration depth of K-, Co-, and P-substituted BaFe2As2

Comprehensive Eliashberg analysis of microwave conductivity and penetration depth of K-, Co-, and P-substituted BaFe2As2

Effects of disorder induced by heavy-ion irradiation on (Ba1−x K x )Fe2As2 single crystals, within the three-band Eliashberg s± wave model

A multiband Eliashberg‐approach to iron‐based superconductors

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