Superconductivity in Fe-chalcogenides

Chang, Chih‐Kai; Chen, Ta-Kun; Lee, W.C.; Lin, Peihua; Wang, Ming-Jye; Wen, Yu-Chieh; Wu, Phillip M.; Wu, Maw–Kuen

doi:10.1016/j.physc.2015.02.011

Cited by 27 publications

(15 citation statements)

References 136 publications

(154 reference statements)

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“…24. ) There are numerous overviews on both experiment and theory for the IBS, for example see reviews by Johnston [437], Paglione and Greene [438], Stewart [30], Hirschfeld, Mazin and Korshunov [439], Hosono and Kuroki [27], Chang et al [440], Hosono et al [348]. Fig.…”

Section: Introductionmentioning

confidence: 99%

Unconventional superconductivity

Stewart

2017

Advances in Physics

220

165

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Abstract:"Conventional" superconductivity, as used in this review, refers to electron-phonon coupled superconducting electron pairs described by BCS theory. Unconventional superconductivity refers to superconductors where the Cooper pairs are not bound together by phonon-exchange but instead by exchange of some other kind, e. g. spin fluctuations in a superconductor with magnetic order either coexistent or nearby in the phase diagram. Such unconventional superconductivity has been known experimentally since heavy fermion CeCu2Si2, with its strongly correlated 4f electrons, was discovered to superconduct below 0.6 K in 1979. Since the discovery of unconventional superconductivity in the layered cuprates in 1986, the study of these materials saw Tc jump to 164 K by 1994. Further progess in high temperature superconductivity would be aided by understanding the cause of such unconventional pairing. This review compares the fundamental properties of 9 unconventional superconducting classes of materialsfrom 4f-electron heavy fermions to organic superconductors to classes where only three known members exist to the cuprates with over 200 examples -with the hope that common features will emerge to help theory explain (and predict!) these phenomena. In addition, three new emerging classes of superconductors (topological, interfacial -e. g. FeSe on SrTiO3, and H2S under high pressure) are briefly covered, even though their "conventionality" is not yet fully determined.

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Section: Introductionmentioning

confidence: 99%

Unconventional superconductivity

Stewart

2017

Advances in Physics

220

165

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“…The discovery of a relatively high T C ∼ 37 K in an iron chalcogenides AFe 2 Se 2 (A=alkali metal) 5,6 came as a surprise due to a largely different FS topology: no hole pockets at the zone center, leaving only electron pockets at the zone corner without any nesting condition. The overall electronic structure of such chalcogenides resembles that of over-electron-doped iron pnictides.…”

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confidence: 99%

Enhanced superconductivity in surface-electron-doped iron pnictide Ba(Fe1.94Co0.06)2As2

et al. 2016

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“…Many of the layered materials display both hole and electron pockets, respectively located at the Γ and X points of the Brillouin zone. However, KFe 2 As 2 only has hole pockets centered at the Γ point [5,6], while in various iron chalcogenides there are only electron pockets [7]. There is no indication for a clear trend in the transition temperatures as pockets disappear.…”

Section: Introductionmentioning

confidence: 99%

Coulomb problem in iron-based superconductors

König

Coleman

2019

Phys. Rev. B

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We discuss the role of strong Coulomb interactions in iron-based superconductors (FeSCs). The presumed s ± character of these superconductors means that the condensate is not symmetry protected against Coulomb repulsion. Remarkably, the transition temperatures and the excitation gap are quite robust across the large family of iron based superconductors, despite drastic changes in Fermi surface geometry. The Coulomb problem is to understand how these superconductors avoid the strong onsite Coulomb interaction at the iron atoms, while maintaining a robust transition temperature. Within the dominant space of t2g orbitals, on-site repulsion in the FeSCs enforces two linearly independent components of the condensate to vanish. This raises the possibility that iron-based superconductors might adapt their condensate to the Coulomb constraints by rotating the pairing state within the large manifold of entangled, extended s-wave gap functions with different orbital and momentum space structure. We examine this "orbital and k-space flexibility" (OKF) mechanism using both Landau theory and microscopic calculations within a multi-orbital t-J model. Based on our results, we conclude that OKF necessitates a large condensate degeneracy. One interesting possibility raised by our results, is that a resolution to the Coulomb problem in FeSC might require a reconsideration of triplet pairing.

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Superconductivity in Fe-chalcogenides

Cited by 27 publications

References 136 publications

Unconventional superconductivity

Unconventional superconductivity

Enhanced superconductivity in surface-electron-doped iron pnictide Ba(Fe1.94Co0.06)2As2

Coulomb problem in iron-based superconductors

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