First-principles study of the electronic structure of iron-selenium: Implications for electron-phonon superconductivity

Koufos, Alexander P.; Papaconstantopoulos, D. A.; Mehl, Michael J.

doi:10.1103/physrevb.89.035150

Cited by 25 publications

(7 citation statements)

References 30 publications

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“…In addition, recent photoemission data show a formation of the lower Hubbard-band satellite at about −2 eV in bulk FeSe which is absent in density functional theory (DFT) [22,24]. Furthermore, computations of the lattice parameters of iron-based superconductors within DFT highlight peculiar deviations with experiments, not captured by standard band structure methods [23,25]. All this suggests a complex interplay between electronic correlations and the lattice, implying the crucial importance of the effect of electronic correlations in FeCh.…”

Section: Introductionmentioning

confidence: 99%

Correlation strength, Lifshitz transition, and the emergence of a two-dimensional to three-dimensional crossover in FeSe under pressure

et al. 2018

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We report a detailed theoretical study of the electronic structure, spectral properties, and lattice parameters of bulk FeSe under pressure using a fully charge self-consistent implementation of the density functional theory plus dynamical mean-field theory method (DFT+DMFT). In particular, we perform a structural optimization and compute the evolution of the lattice parameters (volume, c/a ratio, and the internal z position of Se) and the electronic structure of the tetragonal (space group P 4/nmm) unit cell of paramagnetic FeSe. Our results for the lattice parameters obtained by structural optimization of FeSe using DFT+DMFT are in good quantitative agreement with experiment. The c/a ratio is slightly overestimated by about 3 %, presumably due to the absence of the van der Waals interactions between the FeSe layers in our calculations. The lattice parameters determined within nonmagnetic DFT are off the experimental values by a remarkable ∼6-15 %, implying a crucial importance of electron correlations in determining the correct lattice properties of FeSe. Upon compression to 10 GPa, the c/a ratio and the lattice volume show a linear-like decrease by 2 and 10 %, respectively, while the Se z coordinate weakly increases by ∼2 %. Most importantly, our results reveal a topological change of the Fermi surface (Lifshitz transition) which is accompanied by a two-to three-dimensional crossover. Our results indicate a small reduction of the quasiparticle mass renormalization m * /m by about 5 % for the e and less than 1 % for the t2 states, as compared to ambient pressure. The behavior of the momentum-resolved magnetic susceptibility χ(q) shows no topological changes of magnetic correlations under pressure, but demonstrates a reduction of the degree of the in-plane (π, π) stripe-type nesting. Our results for the electronic structure and lattice parameters of FeSe are in good qualitative agreement with recent experiments on its isoelectronic counterpart FeSe1−xSx.

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Section: Introductionmentioning

confidence: 99%

Correlation strength, Lifshitz transition, and the emergence of a two-dimensional to three-dimensional crossover in FeSe under pressure

et al. 2018

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“…By approximating the Coulomb repulsion through the pseudopotential term µ * [32], we estimate that for µ * = 0.1 and 0.14, T c =33 K and 26 K, respectively. However, the presence of an additional low-energy attractive channel due to the intrinsic EPI in FeSe monolayer [42][43][44], although not sufficient to mediate the high-T c on its own, can balance the T c decrease due to Coulomb repulsion. We find that inclusion of the intrinsic EPI of freestanding monolayer FeSe [44] leads to T c =57 K and 51 K for µ * = 0.1 and 0.14, respectively.…”

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confidence: 99%

Multiband full-bandwidth anisotropic Eliashberg theory of interfacial electron-phonon coupling and high−Tc superconductivity in FeSe
Aperis
¹
,
Oppeneer
²

2018
Phys. Rev. B
41
10
77
1
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We examine the impact of interfacial phonons on the superconducting state of FeSe/SrTiO3 developing a materials' specific multiband, full bandwidth, anisotropic Eliashberg theory for this system. Our selfconsistent calculations highlight the importance of the interfacial electron-phonon interaction, which is hidden behind the seemingly weak coupling constant λm=0.4, in mediating the high-Tc, and explain other puzzling experimental observations like the s-wave symmetry and replica bands. We discover that the formation of replica bands has a Tc decreasing effect that is nevertheless compensated by deep Fermi-sea Cooper pairing which has a Tc enhancing effect. We predict a strong coupling dip-hump signature in the tunneling spectra due to the interfacial coupling.Superconductivity in monolayer-thick FeSe on SrTiO 3 reaches amazingly high transition temperatures of typically T c =50-70 K [1-6] and up to 100 K [7], much higher than the 8-K value of bulk FeSe [8]. A coupling between SrTiO 3 phonons and FeSe electrons occurs at the FeSe/SrTiO 3 interface, which manifests itself as electron replica bands [6]. The value of this coupling is estimated by experiments to be around 0.4, thus it is commonly believed to moderately enhance T c but not be enough to explain it [6,9,10].The superconducting state in iron-based superconductors is customarily associated with residual spin fluctuations due to the remnant quasi-nesting between electron and hole Fermi sheets that give rise to a sign alternating gap [11]. However, for FeSe/STO the situation is markedly different. Charge transfer at the interface induces electron doping in FeSe [3,4], leading to a distinct Fermi surface consisting of only two electron sheets around the corners of the tetragonal Brillouin zone (M point) [12]. The observed anisotropic superconducting gap has a more conventional form with plain s-wave symmetry [13] and is thus nodeless in the entire Brillouin zone. Furthermore, angular resolved photoemission spectroscopy (ARPES) measurements [6] reveal an interfaceinduced electron-phonon interaction (EPI) between FeSe electrons and polar STO phonons that is strongly peaked at the q=0 phonon wavevector [6,[14][15][16][17][18]. There is growing experimental evidence for the pivotal role of such interfacial phonons in engineering high-T c heterostructures that involve FeSe [5,9,19] or even FeAs [20] monolayers.Although ab initio calculations confirm the existence of small-q phonons as a strictly interfacial phenomenon in FeSe/STO [12,[21][22][23] and indicate the importance of the coupling between substrate phonons and FeSe electrons [24], the estimated low value of the electron-phonon coupling constant (λ ≤ 0.4) has been widely considered insufficient to explain the impressive T c enhancement unless another, dominant pairing mechanism is at play [6]. On the other hand, Eliashberg calculations within a single band model suggest that interfacial phonons may lead to the high T c with a coupling of merely half of that estimated by experiments [25]. However, a mater...

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“…53 Recently, the strong electron-phonon interaction has been observed in transition metal chalcogenides, which indicates the importance of electron-phonon coupling for high temperature superconductivity. 32,33,54,55 PdS as a transition metal chalcogenide, should be also an electron-phonon coupled superconductor.…”

Section: Resultsmentioning

confidence: 99%

Pressure-induced superconductivity in palladium sulfide

Chen

Pang

et al. 2018

J. Phys.: Condens. Matter

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An extended study on PdS is carried out with the measurements of the resistivity, Hall coefficient, Raman scattering, and x-ray diffraction at high pressures up to 42.3 GPa. With increasing pressure, superconductivity is observed accompanying with a structural phase transition at around 19.5 GPa. The coexistence of semiconducting and metallic phases observed at normal state is examined by the Raman scattering and x-ray diffraction between 19.5 and 29.5 GPa. After that, only the metallic normal state maintains with an almost constant superconducting transition temperature. The similar evolution between the superconducting transition temperature and carrier concentration with pressure supports the phonon-mediated superconductivity in this material. These results highlight the important role of pressure played in inducing superconductivity from these narrow band-gap semiconductors.

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First-principles study of the electronic structure of iron-selenium: Implications for electron-phonon superconductivity

Cited by 25 publications

References 30 publications

Correlation strength, Lifshitz transition, and the emergence of a two-dimensional to three-dimensional crossover in FeSe under pressure

Correlation strength, Lifshitz transition, and the emergence of a two-dimensional to three-dimensional crossover in FeSe under pressure

Multiband full-bandwidth anisotropic Eliashberg theory of interfacial electron-phonon coupling and high−Tc superconductivity in FeSe
Aperis
¹
,
Oppeneer
²

2018
Phys. Rev. B
41
10
77
1
View full text Add to dashboard Cite

Pressure-induced superconductivity in palladium sulfide

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First-principles study of the electronic structure of iron-selenium: Implications for electron-phonon superconductivity

Cited by 25 publications

References 30 publications

Correlation strength, Lifshitz transition, and the emergence of a two-dimensional to three-dimensional crossover in FeSe under pressure

Correlation strength, Lifshitz transition, and the emergence of a two-dimensional to three-dimensional crossover in FeSe under pressure

Multiband full-bandwidth anisotropic Eliashberg theory of interfacial electron-phonon coupling and high−Tc superconductivity in FeSeAperis1, Oppeneer2 2018Phys. Rev. B4110771View full textAdd to dashboardCite

Pressure-induced superconductivity in palladium sulfide

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Multiband full-bandwidth anisotropic Eliashberg theory of interfacial electron-phonon coupling and high−Tc superconductivity in FeSe
Aperis
¹
,
Oppeneer
²

2018
Phys. Rev. B
41
10
77
1
View full text Add to dashboard Cite