Temperature dependence of the superfluid density as a probe for multiple gaps in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>Ba</mml:mi><mml:mo>(</mml:mo><mml:mi>Fe</mml:mi></mml:mrow><mml:mrow><mml:mn>0.9</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi mathvariant="normal">Co</mml:mi></mml:mrow><mml:mrow><mml:mn>0.1</mml:mn></mml:mrow></mml:msub><mml:mo>)</mml:mo><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mi mathvariant="no

Karakozov, A. E.; Zapf, Sina; Gorshunov, B.; Ponomarev, Ya. G.; Magnitskaya, M. V.; Жукова, Е. С.; Anzin, V. B.; Haindl, S.

doi:10.1103/physrevb.90.014506

Cited by 11 publications

(17 citation statements)

References 41 publications

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“…An advanced multiband Eliashberg analysis along these lines is necessary to reconsider/check the strong coupling results mentioned above. A weak ‐coupling interband regime within two‐ and three ‐band descriptions has also been found for Co ‐doped Ba‐122 , based on specific heat and optical data. These works found a non ‐BCS shape of the T ‐dependent small gap functions, which affected the behavior of the penetration depth, in contrast to a BCS ‐like shape expected for a dominant interband coupling.…”

Section: Weak Versus Strong Coupling In Fe ‐Based Superconductorsmentioning

confidence: 60%

Constraints on the total coupling strengthto bosons in the iron based superconductors

Drechsler

Johnston

Grinenko

et al. 2017

Phys. Status Solidi B

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Despite the fact that the Fe-based superconductors (FeSCs) were discovered nearly ten years ago, the community is still devoting a tremendous effort towards elucidating their relevant microscopic pairing mechanism(s) and interactions. At present, there is still no consistent interpretation of their normal state properties, where the strength of the electron-electron interaction and the role of correlation effects are under debate. Here, we examine several common materials and illustrate various problems and concepts that are generic for all FeSCs. Based on empirical observations and qualitative insight from density functional theory, we show that the superconducting and low-energy thermodynamic properties of the FeSCs can be described semi-quantitively within multiband Eliashberg theory. We account for an important high-energy mass renormalization phenomenologically, and in agreement with constraints provided by thermodynamic, optical, and angle-resolved photoemission data. When seen in this way, all FeSCs with T c < 40 K studied so far are found to belong to an intermediate coupling regime. This finding is in contrast to the strong coupling scenarios proposed in the early period of the FeSC history. We also discuss several related issues, including the role of band shifts as measured by the positions of van Hove singularities, and the nature of a recently suggested quantum critical point in the strongly hole-doped systems AFe 2 As 2 (A = K, Rb, Cs). Using high-precision full relativistic GGA-band structure calculations, we arrive at a somewhat milder mass renormalization in comparison with previous studies. From the calculated mass anisotropies of all Fermi surface sheets, only the ε-pocket near the corner of the BZ is compatible with the experimentally observed anisotropy of the upper critical field, pointing to its dominant role in the superconductivity of these three compounds.

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Section: Weak Versus Strong Coupling In Fe ‐Based Superconductorsmentioning

confidence: 60%

Constraints on the total coupling strengthto bosons in the iron based superconductors

Drechsler

Johnston

Grinenko

et al. 2017

Phys. Status Solidi B

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“…Penetration depth measurements for Co‐doped BaFe

_{2}

_{2}

thin films by a two‐coil mutual inductance apparatus have confirmed values in the range of

λ false(0 false)

= 350–430 nm and, therefore, are fully comparable to values obtained for crystals (). The temperature‐dependence of the superfluid density revealed by terahertz spectroscopy in BaFe

_{2}

_{2}

was modeled by a two‐band (), and later, by a three‐band model (). Both of the mentioned experiments have found evidence for a small superconducting gap with

2 Δ false(0 false) / k_{B} T_{c} \approx

2.1–2.2.…”

Section: Fundamental Studies On Iron Pnictide Thin Filmsmentioning

confidence: 99%

Iron pnictide thin films: Synthesis and physics

Haindl

Kidszun

Kampert

2016

Physica Status Solidi (b)

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Superconducting thin films play a prominent role in applications of superconductivity and provide an essential source for studying physical phenomena. Here, we summarize the activities for iron pnictide thin films with a focus on the German Special Priority Programme from 2009 until today. The quick availability of such films after the discovery of superconductivity in the iron‐based superconductors enabled a number of experiments. After a general introduction and a brief historical overview we focus on film synthesis of iron pnictides by a two‐step method and by pulsed laser deposition, the assessment of their application potential, the upper critical fields in iron oxypnictides of F‐doped LaOFeAs and F‐doped Sm1−xLaxOFeAs and on superconductivity in Fe/BaFe2As2 heterostructures.

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“…This is somewhat surprising for two reasons. First, the curve has not been refined in any way, and second, this is a simple superposition of two single-band BCS models and not a more sophisticated two-band model of superconductivity that considers both intraband as well as interband pairing [64][65][66]. On the other hand, since this approach appears to work rather well, we speculate that the large difference in the scattering rates in the two bands allows for this simpler interpretation.…”

Section: Multiband Superconductormentioning

confidence: 99%

FeTe0.55Se0.45: A multiband superconductor in the clean and dirty limit

et al. 2015

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The detailed optical properties of the multiband iron-chalcogenide superconductor FeTe0.55Se0.45 have been reexamined for a large number of temperatures above and below the critical temperature Tc = 14 K for light polarized in the a-b planes. Instead of the simple Drude model that assumes a single band, above Tc the normal-state optical properties are best described by the two-Drude model that considers two separate electronic subsystems; we observe a weak response (ωp,D;1 3000 cm −1 ) where the scattering rate has a strong temperature dependence (1/τD,1 32 cm −1 for T Tc), and a strong response (ωp,D;2 14 500 cm −1 ) with a large scattering rate (1/τD,2 1720 cm −1 ) that is essentially temperature independent. The multiband nature of this material precludes the use of the popular generalized-Drude approach commonly applied to single-band materials, implying that any structure observed in the frequency dependent scattering rate 1/τ (ω) is spurious and it cannot be used as the foundation for optical inversion techniques to determine an electron-boson spectral function α 2 F (ω). Below Tc the optical conductivity is best described using two superconducting optical gaps of 2∆1 45 and 2∆2 90 cm −1 applied to the strong and weak responses, respectively. The scattering rates for these two bands are vastly different at low temperature, placing this material simultaneously in both clean and dirty limit. Interestingly, this material falls on the universal scaling line initially observed for the cuprate superconductors.

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Temperature dependence of the superfluid density as a probe for multiple gaps inBa(Fe0.9Co0.1)2
A. E. Karakozov
¹
,
Sina Zapf
²
,
B. Gorshunov
³

et al.

Cited by 11 publications

References 41 publications

Constraints on the total coupling strengthto bosons in the iron based superconductors

Constraints on the total coupling strengthto bosons in the iron based superconductors

Iron pnictide thin films: Synthesis and physics

FeTe0.55Se0.45: A multiband superconductor in the clean and dirty limit

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Temperature dependence of the superfluid density as a probe for multiple gaps inBa(Fe0.9Co0.1)2A. E. Karakozov1, Sina Zapf2, B. Gorshunov3 et al.

Cited by 11 publications

References 41 publications

Constraints on the total coupling strengthto bosons in the iron based superconductors

Constraints on the total coupling strengthto bosons in the iron based superconductors

Iron pnictide thin films: Synthesis and physics

FeTe0.55Se0.45: A multiband superconductor in the clean and dirty limit

Contact Info

Product

Resources

About

Temperature dependence of the superfluid density as a probe for multiple gaps inBa(Fe0.9Co0.1)2
A. E. Karakozov
¹
,
Sina Zapf
²
,
B. Gorshunov
³

et al.