Band structure of SrFeAsF and CaFeAsF—the base phases of a new group of oxygen-free FeAs superconductors

Shein, I. R.; Ivanovskiĭ, A. L.

doi:10.1134/s0021364008220104

Cited by 15 publications

(10 citation statements)

References 19 publications

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“…3(a) and (b), respectively, which are in good agreement with previous report. 34 Firstly we examine the energy dispersions between high symmetric k-points of Γ and Z, there is no band intersects across the Fermi level. This result indicates the absence of the 3D Fermi pocket around the Z point.…”

Section: Discussionmentioning

confidence: 99%

Strong anisotropy effect in an iron-based superconductor CaFe_0.882Co_0.118AsF

Ma¹,

Ji²,

Hu³

et al. 2017

Supercond. Sci. Technol.

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The anisotropy of the Fe-based superconductors is much smaller than that of the cuprates and the theoretical calculations. A credible understanding for this experimental fact is still lacking up to now. Here we experimentally study the magnetic-field-angle dependence of electronic resistivity in the superconducting phase of iron-based superconductor CaFe0.882Co0.118AsF, and find the strongest anisotropy effect of the upper critical field among the iron-based superconductors based on the framework of Ginzburg-Landau theory. The evidences of energy band structure and charge density distribution from electronic structure calculations demonstrate that the observed strong anisotropic effect mainly comes from the strong ionic bonding in between the ions of Ca 2+ and F − , which weakens the interlayer coupling between the layers of FeAs and CaF. This finding provides a significant insight into the nature of experimentally observed strong anisotropic effect of electronic resistivity, and also paves an avenue to design exotic two dimensional artificial unconventional superconductors in future.

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Section: Discussionmentioning

confidence: 99%

Strong anisotropy effect in an iron-based superconductor CaFe_0.882Co_0.118AsF

Ma¹,

Ji²,

Hu³

et al. 2017

Supercond. Sci. Technol.

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“…The DOS at ε F , N(0), is 4.5 eV −1 in LiFeAs (per unit cell of two formula units), which is comparable to that of many other FeSCs. [31][32][33][34][35][36] In MgFeGe N(0) = 5.7 eV −1 , 20% larger than in LiFeAs.…”

Section: Density Of Statesmentioning

confidence: 99%

Contrast of LiFeAs with Isostructural, Isoelectronic, and Non-superconducting MgFeGe

Rhee

Pickett

2013

J. Phys. Soc. Jpn.

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Stoichiometric LiFeAs at ambient pressure is an 18 K superconductor while isostructural, isoelectronic MgFeGe does not superconduct, despite their extremely similar electronic structures. To investigate possible sources of this distinctively different superconducting behavior, we quantify the differences using first principles density functional theory. Total Fe 3d occupations are identical, with individual 3d orbital occupations differing by no more than 0.015. However, a redistribution of bands just above the Fermi level ε F provides an important distinction, with more Fe-derived states within 0.5 eV of the Fermi level and a higher N(ε F ) in MgFeGe. For many mechanisms these features would enhance the tendency toward superconductivity by providing more Cooper pairs (in MgFeGe), but the tendency toward magnetic instability might be more important. Two of the five Fermi surfaces differ between LiFeAs and MgFeGe, but still lead to similar q-dependencies of susceptibilities χ 0 (q) including the familiar broad peak at (π, π). The larger χ 0 (q) in MgFeGe, by 10-15% throughout the zone, leads us to tentatively identify this proximity to magnetic instability as the feature underlying the absence of superconductivity in MgFeGe. Another significant difference is the 2.5% difference of the in-plane lattice constant, positioning LiFeAs as a chemically compressed version of MgFeGe. This has possible significance since certain Fe pnictides display pressure-induced superconductivity.

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“…There are plenty of papers on LDA band structure of La111 [33,34,35], LaOFeP [36], RE111 series [37], BaFe 2 As 2 [38,39,40], LiFeAs [41,42], (Sr,Ca)FFeAs [43,44], Sr42622 [45]. Electronic structure of Fe(S,Se,Te) materials was discussed in Ref.…”

Section: Electronic Structurementioning

confidence: 99%

Iron based superconductors: Pnictides versus chalcogenides

Sadovskiǐ

Kuchinskiǐ

Некрасов

2012

Journal of Magnetism and Magnetic Materials

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a b s t r a c tWe present a brief review of the present day situation with studies of high-temperature superconductivity in iron pnictides and chalcogenides. Recent discovery of superconductivity with T c 4 30 K in A x Fe 2 À x/2 Se 2 (A ¼ K, Cs, Tl, etc) represents the major new step in the development of new concepts in the physics of Fe-based high-temperature superconductors. We compare LDA and ARPES data on the band structure and Fermi surfaces of novel superconductors and those of the previously studied FeAs superconductors, especially isostructural 122-superconductors like BaFe 2 As 2 . It appears that electronic structure of new superconductors is rather different from that of FeAs 122-systems. In particular, no nesting properties of electron and hole-like Fermi surfaces is observed, casting doubts on most popular theoretical schemes of Cooper pairing for these systems. Doping of novel materials is extremely important as a number of topological transitions of Fermi surface near the G point in the Brillouin zone are observed for different doping levels. The discovery of Fe vacancies ordering and antiferromagnetic (AFM) ordering at pretty high temperatures (T N 4 500 K), much exceeding superconducting T c makes these systems unique antiferromagnetic superconductors with highest T N observed up to now. This poses very difficult problems for theoretical understanding of superconductivity. We discuss the role of both vacancies and AFM ordering in transformations of band structure and Fermi surfaces, as well as their importance for superconductivity. In particular, we show that system remains metallic with unfolded Fermi surfaces quite similar to that in paramagnetic state. Superconducting transition temperature T c of new superconductors is discussed within the general picture of superconductivity in multiple band systems. It is demonstrated that both in FeAs-superconductors and in new FeSesystems the value of T c correlates with the value of the total density of states (DOSs) at the Fermi level.

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Band structure of SrFeAsF and CaFeAsF—the base phases of a new group of oxygen-free FeAs superconductors

Cited by 15 publications

References 19 publications

Strong anisotropy effect in an iron-based superconductor CaFe_0.882Co_0.118AsF

Strong anisotropy effect in an iron-based superconductor CaFe_0.882Co_0.118AsF

Contrast of LiFeAs with Isostructural, Isoelectronic, and Non-superconducting MgFeGe

Iron based superconductors: Pnictides versus chalcogenides

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Band structure of SrFeAsF and CaFeAsF—the base phases of a new group of oxygen-free FeAs superconductors

Cited by 15 publications

References 19 publications

Strong anisotropy effect in an iron-based superconductor CaFe0.882Co0.118AsF

Strong anisotropy effect in an iron-based superconductor CaFe0.882Co0.118AsF

Contrast of LiFeAs with Isostructural, Isoelectronic, and Non-superconducting MgFeGe

Iron based superconductors: Pnictides versus chalcogenides

Contact Info

Product

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Strong anisotropy effect in an iron-based superconductor CaFe_0.882Co_0.118AsF

Strong anisotropy effect in an iron-based superconductor CaFe_0.882Co_0.118AsF