Fermi Surface, Pressure-Induced Antiferromagnetic Order, and Superconductivity in FeSe

Ishizuka, Jun; Yamada, Takemi; Yanagi, Yousuke; Ōno, Yoshiaki

doi:10.7566/jpsj.87.014705

Cited by 11 publications

(11 citation statements)

References 67 publications

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“…However, electronic interactions and associated self-energy effects are known to be important in FeSe, constituting an example of a Hund's metal [25]. Important properties of Hund's metals include the existence of orbital dependent mass renormalizations [43][44][45], and an associated redistribution of the relative importance of different orbital dependent scattering channels in the spin susceptibility [46].…”

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confidence: 99%

Anisotropic spin fluctuations in detwinned FeSe

et al. 2019

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Superconductivity in FeSe emerges from a nematic phase that breaks four-fold rotational symmetry in the iron plane. This phase may arise from orbital ordering, spin fluctuations, or hidden magnetic quadrupolar order. Here we use inelastic neutron scattering on a mosaic of single crystals of FeSe detwinned by mounting on a BaFe2As2 substrate to demonstrate that spin excitations are most intense at the antiferromagnetic wave vectors Q AF = (±1, 0) at low energies E = 611 meV in the normal state. This two-fold (C2) anisotropy is reduced at lower energies 3-5 meV, indicating a gapped four-fold (C4) mode. In the superconducting state, however, the strong nematic anisotropy is again reflected in the spin resonance (E = 3.7 meV) at QAF with incommensurate scattering around 5-6 meV. Our results highlight the extreme electronic anisotropy of the nematic phase of FeSe and are consistent with a highly anisotropic superconducting gap driven by spin fluctuations.

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confidence: 99%

Anisotropic spin fluctuations in detwinned FeSe

et al. 2019

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“…These small FSs and the lowenergy bandstructure have not still been reproduced by the density-functional theory (DFT) [37], DFT+U [38], the dynamical mean field theory (DMFT) [18][19][20]39] and quasiparticle self-consistent GW (QSGW ) [40]. Several studies based on adjusted models to reproduce the low-energy bands of angle resolved photoemission spectroscopy (ARPES) [31] can explain the enhancement of orbital and magnetic fluctuations in T -P phase [41][42][43].…”

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Multipolar nematic state of nonmagnetic FeSe based on the DFT+$U$

Yamada,

Tohyama

2021

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Clarifying the origin of nematic state in FeSe is one of urgent problems in the field of iron-based superconductivity. Motivated by the discovery of a nematic solution in the density-functional theory implemented by on-site Coulomb interaction (DFT+U ) [X. Long et al., npj Quantum Mater. 5, 50 (2020)], we reexamine the U dependence of electronic states in the nonmagnetic normal state of FeSe and perform full multipolar analyses for the nematic state. We find that with increasing U the normal state experiences a topological change of the Fermi surfaces before the emergence of a nematic ground state. The resulting nematic ground state is a multipolar state having both antiferro-hexadecapoles in the E-representation and ferro-multipoles in the B2-representation on each Fe site. Cooperative coupling between the E and B2 multipoles in local coordinate with the D 2d point group will play an important role in the formation of the dxz, dyz orbital-splitting nematic state not only in FeSe but also in other iron pnictides.

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“…We confirmed that the geometric term is dominant in this region. To reproduce the Fermi surfaces of FeSe observed in experiments, we slightly modify the hopping parameters given by the first-principles calculation 68,78,79 . For this purpose, the energies of the d xy -orbital band and the d xz/yz -orbital band are shifted by (−0.28, 0, 0.20) and (−0.27, 0, 0.13) at (Γ,X,M ) points in the folded Brillouin zone, respectively.…”

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confidence: 99%

“…To reproduce the experimentally observed Fermi surfaces of FeSe, we take into account additional hopping parameters in addition to those given by the WIEN2k code, in a similar manner to Refs. 68,78,79 (see Appendix. C for details).…”

Section: B Fesementioning

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Thermodynamic electric quadrupole moments of nematic phases from first-principles calculation

Kitamura,

Ishizuka,

Daido

et al. 2021

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The electronic nematic phase emerging with spontaneous rotation symmetry breaking is a central issue of modern condensed matter physics. In particular, various nematic phases in iron-based superconductors and high-Tc cuprate superconductors are extensively studied recently. Electric quadrupole moments (EQMs) are one of the order parameters characterizing these nematic phases in a unified way, and elucidating EQMs is a key to understanding these nematic phases. However, the quantum-mechanical formulation of the EQMs in crystals is a nontrivial issue because the position operators are non-periodic and unbound. Recently, the EQMs have been formulated by local thermodynamics, and such thermodynamic EQMs may be used to characterize the fourfold rotation symmetry breaking in materials. In this paper, we calculate the thermodynamic EQMs in iron-based superconductors LaFeAsO and FeSe as well as a cuprate superconductor La2CuO4 by a firstprinciples calculation. We show that owing to the orbital degeneracy the EQMs in iron-based superconductors are mainly determined by the geometric properties of wave functions. This result is in sharp contrast to the cuprate superconductor, in which the EQMs are dominated by distortion of the Fermi surface.

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Fermi Surface, Pressure-Induced Antiferromagnetic Order, and Superconductivity in FeSe

Cited by 11 publications

References 67 publications

Anisotropic spin fluctuations in detwinned FeSe

Anisotropic spin fluctuations in detwinned FeSe

Multipolar nematic state of nonmagnetic FeSe based on the DFT+$U$

Thermodynamic electric quadrupole moments of nematic phases from first-principles calculation

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