Fermi surface pockets in electron-doped iron superconductor by Lifshitz transition

Rodríguez, José; Melendrez, Ronald

doi:10.1088/2399-6528/aae0dc

Cited by 10 publications

(49 citation statements)

References 47 publications

(180 reference statements)

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“…Thus, it demonstrated that a synergistic effect between possible spin fluctuations and enhanced EPI results in such high T c in FeSe/STO. It is worth noting that theorists could qualitatively describe the Fermi surface, hidden magnetic order, replica bands, and the superconductivity isotropic Cooper pairs in heavily electron-doped FeSe by an extended Hubbard model [99,100]. Such explanations could deepen the understanding of the superconducting mechanism and may help us explore more high T c superconductors.…”

Section: Superconductivity Of Fese Filmmentioning

confidence: 99%

“…It also implies that a higher T c will appear in the FeSe film if the lattice constants are expanded and higher electronic doping is introduced. Rebec et al compared the T c and the scale of superconducting gap in 60 unit-cell FeSe/STO (001), SUC FeSe/STO (001), and 3 UC FeSe/STO (001) coated by potassium atoms and SUC FeSe/TiO 2 (100). By analyzing the ARPES results, they found that electron doping plays an important role in inducing high T c [93].…”

Section: Superconductivity Of Fese Filmmentioning

confidence: 99%

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Highly-Tunable Crystal Structure and Physical Properties in FeSe-Based Superconductors

et al. 2019

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Here, crystal structure, electronic structure, chemical substitution, pressure-dependent superconductivity, and thickness-dependent properties in FeSe-based superconductors are systemically reviewed. First, the superconductivity versus chemical substitution is reviewed, where the doping at Fe or Se sites induces different effects on the superconducting critical temperature (T c ). Meanwhile, the application of high pressure is extremely effective in enhancing T c and simultaneously induces magnetism. Second, the intercalated-FeSe superconductors exhibit higher T c from 30 to 46 K. Such an enhancement is mainly caused by the charge transfer from the intercalated organic and inorganic layer. Finally, the highest T c emerging in single-unit-cell FeSe on the SrTiO 3 substrate is discussed, where electron-phonon coupling between FeSe and the substrate could enhance T c to as high as 65 K or 100 K. The step-wise increment of T c indicates that the synergic effect of carrier doping and electron-phonon coupling plays a critical role in tuning the electronic structure and superconductivity in FeSe-based superconductors.

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Section: Superconductivity Of Fese Filmmentioning

confidence: 99%

Section: Superconductivity Of Fese Filmmentioning

confidence: 99%

Highly-Tunable Crystal Structure and Physical Properties in FeSe-Based Superconductors

et al. 2019

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“…Recent theoretical work suggests that the "rings" and "diamonds" of spin excitations observed in electron-doped FeSe at the checkerboard wavevector are due to proximity to a hidden spin-density wave (hSDW) state 17,18 . Here, the sign of the ordered magnetic moment alternates between the principal d+ = (d xz + id yz )/ √ 2 and d− = (d xz − id yz )/ √ 2 orbitals of the iron atom, as well as between the "white" and the "black" sites on the checkerboard of iron atoms 19,20 .…”

Section: Introductionmentioning

confidence: 99%

“…It has recently been shown by the author and a co-worker that fluctuation-exchange with Goldstone modes associated with such hidden magnetic order results in a Lifshitz transition to electron/hole Fermi surface pockets at the corner of the folded Brillouin zone 18 . (See Fig.…”

Section: Introductionmentioning

confidence: 99%

“…Below, we shall reveal the nature of spin excitations in the hidden SDW state within an extended Hubbard model over a square lattice of iron atoms that includes only the principal 3d xz and 3d yz orbitals of iron superconductors 18 . In particular, the dynamical spin susceptibility is computed within a Nambu-Gorkov-type [22][23][24] random phase approximation (RPA) that accounts for perfect nesting of the unrenormalized Fermi surfaces mentioned above.…”

Section: Introductionmentioning

confidence: 99%

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Spin Resonances in Iron-Selenide High-Tc Superconductors by Proximity to Hidden Spin Density Wave

Rodriguez

2020

Preprint

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Recent inelastic neutron scattering studies by Pan et al., Nature Communications 8, 123 (2017), find evidence for spin excitations at energies above the quasi-particle gap in an iron-selenide high-T c superconductor. The momenta of the spin excitations form a diamond around the checkerboard wavevector, Q AF , that is associated with the square lattice of iron atoms that makes up the system.It has been suggested that such a "hollowed-out" spin-excitation spectrum is due to hidden Néel order. We study such a hidden spin-density wave (hSDW) state that results from nested Fermi surfaces at the center and at the corner of the unfolded Brillouin zone. It emerges within mean field theory from an extended Hubbard model over a square lattice of iron atoms that contain the minimal d xz and d yz orbitals. Opposing Néel order exists over the isotropic d+ = d xz + id yz and d− = d xz − id yz orbitals. The dynamical spin susceptibility of the hSDW is computed within the random phase approximation, at perfect nesting. Unobservable Goldstone modes that disperse acoustically are found at Q AF . A threshold is found in the spectrum of observable spin excitations that forms a "floating ring" at Q AF also. The ring threshold moves down in energy toward zero with increasing Hund's Rule coupling, while it moves up in energy with increasing magnetic frustration.Comparison with the normal-state features of the spin-excitation spectrum shown by electrondoped iron selenide is made. Also, recent predictions of a Lifshitz transition from the nested Fermi surfaces to Fermi surface pockets at the corner of the folded Brillouin zone will be discussed.

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Prediction of antiferromagnetism in barium chromium phosphide confirmed after synthesis

Jishi

Rodríguez

Haugan

et al. 2019

J. Phys.: Condens. Matter

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We have carried out density-functional theory (DFT) calculations for the chromium-pnictide BaCr 2 P 2 , which is structurally analogous to BaFe 2 As 2 , a parent compound for iron-pnictide superconductors. Evolutionary methods combined with DFT predict that the chromium analog has the same crystal structure as the latter. DFT also predicts Néel antiferromagnetic order on the chromium sites. Comparison with a simple electron-hopping model over a square lattice of chromium atoms suggests that it is due to residual nesting of the Fermi surfaces. We have confirmed the DFT predictions directly after the successful synthesis of polycrystalline samples of BaCr 2 P 2 . X-ray diffraction recovers the predicted crystal structure to high accuracy, while magnetic susceptibility and specific-heat measurements are consistent with a transition to an antiferromagnetically ordered state below T N ∼ 60 K.

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Fermi surface pockets in electron-doped iron superconductor by Lifshitz transition

Cited by 10 publications

References 47 publications

Highly-Tunable Crystal Structure and Physical Properties in FeSe-Based Superconductors

Highly-Tunable Crystal Structure and Physical Properties in FeSe-Based Superconductors

Spin Resonances in Iron-Selenide High-Tc Superconductors by Proximity to Hidden Spin Density Wave

Prediction of antiferromagnetism in barium chromium phosphide confirmed after synthesis

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