A calorimetric investigation of RbFe<sub>2</sub>As<sub>2</sub> single crystals

Khim, Seunghyun; Aswartham, Saicharan; Grinenko, V.; Efremov, D. V.; Blum, Christian; Steckel, Frank; Grüner, Daniel; Wolter, A. U. B.; Drechsler, S.‐L.; Heß, Christian; Wurmehl, S.; Büchner, B.

doi:10.1002/pssb.201600208

Cited by 11 publications

(9 citation statements)

References 53 publications

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“…For the sake of simplicity a vanishing pair ‐breaking for

Θ = 0

has been adopted in our analysis by Eq. (6), in accord with the experimental data within the error bars. Here,

Θ

measures the tilting of the external field direction from the c ‐axis and

H_{c 2, italicab}^{orb}

is the orbital limited upper critical field without paramagnetic effects and

μ false(T false)

denotes the pair ‐breaking parameter (notice that

μ false(0 false) = α_{M} / 1.76

, where

α_{M}

is the frequently used Maki parameter) scaled by the d ‐wave gap function

Δ false(T false)

and the orbital limited Werthamer–Helfand–Hohenberg (WHH) upper critical field

…”

Section: Afe2as2 a = K Rb Cs Puzzles –A Challenge For Theorysupporting

confidence: 86%

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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“…For the sake of simplicity a vanishing pair ‐breaking for

Θ = 0

has been adopted in our analysis by Eq. (6), in accord with the experimental data within the error bars. Here,

Θ

measures the tilting of the external field direction from the c ‐axis and

H_{c 2, italicab}^{orb}

is the orbital limited upper critical field without paramagnetic effects and

μ false(T false)

denotes the pair ‐breaking parameter (notice that

μ false(0 false) = α_{M} / 1.76

, where

α_{M}

is the frequently used Maki parameter) scaled by the d ‐wave gap function

Δ false(T false)

and the orbital limited Werthamer–Helfand–Hohenberg (WHH) upper critical field

…”

Section: Afe2as2 a = K Rb Cs Puzzles –A Challenge For Theorysupporting

confidence: 86%

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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“…The behavior of heat capacity observed here was found experimentally in many multi-band materials like iron-based superconductors from 11 [71,72], 111 [73][74][75], or 122 family [52,[76][77][78][79][80][81][82][83][84][85][86][87], MgB 2 -classical two band superconductor [88] and many others (e.g., 2H-Pd x TaSe 2 [89], Lu 2 Fe 3 Si 5 [90] or NbS 2 [91]). One needs to stress that the unconventional superconductors (with the gap symmetry other than s-wave) is characterized by a different dependence of C vs. T/T c .…”

Section: Specific Heatsupporting

confidence: 62%

Effects of Pair-Hopping Coupling on Properties of Multi-Band Iron-Based Superconductors

2020

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A variety of superconducting materials exhibit multi-band behavior in a form of multicomponent Fermi surfaces. By using a two-band model with a pair hopping, we explain how the interband coupling affects the physical properties of multi-band superconductors. We determine the temperature dependence of the superconducting gap and the specific heat, which strongly diverge from the BCS-type behavior. The anisotropic gap for the system with the mixed gap symmetry is found. Additionally, the spectral function and density of states are significantly modified by the inter-orbital interactions. The results obtained for different symmetries of the order parameter are in a good agreement with the experimental findings for the iron-based superconductors and other multi-band systems.

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“…Given that Fe likely has a leading effect on the high temperature superconductivity in doped BFA, the effect of partial substitution of Fe on superconducting properties in general, and on their anisotropy evolution remains unaddressed. The heavily hole-doped compounds differ from their optimally doped counterparts by the presence of particularly strong electronic correlations [17], which is seen in their substantially larger reported mass enhancements compared to those of the optimally doped compounds. For instance, it is well established that CaFe 2 As 2 is less correlated than KFe 2 As 2 at ambient pressure [18,19].…”

Section: Introductionmentioning

confidence: 97%

High-pressure effects on isotropic superconductivity in the iron-free layered pnictide superconductor BaPd2As2

et al. 2018

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While the layered 122 iron arsenide superconductors are highly anisotropic, unconventional, and exhibit several forms of electronic orders that coexist or compete with superconductivity in different regions of their phase diagrams, we find in the absence of iron in the structure that the superconducting characteristics of the end member BaPd2As2 are surprisingly conventional. Here we report on a complementary measurements of specific heat, magnetic susceptibility, resistivity measurements, Andreev spectroscopy and synchrotron high pressure X-ray diffraction measurements supplemented with theoretical calculations for BaPd2As2. Its superconducting properties are completely isotropic as demonstrated by the critical fields, which do not depend on the direction of the applied field. Under the application of high pressure, Tc is linearly suppressed, which is the typical behaviour of classical phonon-mediated superconductors with some additional effect of a pressure-induced decrease in the electronic density of states and the electron-phonon coupling parameters. Structural changes in the layered BaPd2As2 have been studied by means of angle-dispersive diffraction in a diamond-anvil cell. At 12 GPa and 27.2 GPa we observed pressure induced lattice distortions manifesting as the discontinuity and, hence discontinuity in the Birch-Murnaghan eqation of state. The bulk modulus is B0 = 40(6) GPa below 12 GPa and B0 = 142(3) GPa below 27.2 GPa.

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A calorimetric investigation of RbFe₂As₂ single crystals

Cited by 11 publications

References 53 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

Effects of Pair-Hopping Coupling on Properties of Multi-Band Iron-Based Superconductors

High-pressure effects on isotropic superconductivity in the iron-free layered pnictide superconductor BaPd2As2

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A calorimetric investigation of RbFe2As2 single crystals

Cited by 11 publications

References 53 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

Effects of Pair-Hopping Coupling on Properties of Multi-Band Iron-Based Superconductors

High-pressure effects on isotropic superconductivity in the iron-free layered pnictide superconductor BaPd2As2

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Product

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A calorimetric investigation of RbFe₂As₂ single crystals