Hund Interaction, Spin-Orbit Coupling, and the Mechanism of Superconductivity in Strongly Hole-Doped Iron Pnictides

Vafek, Oskar; Chubukov, Andrey V.

doi:10.1103/physrevlett.118.087003

Cited by 75 publications

(103 citation statements)

References 43 publications

(55 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Consequently a gap at the FS opens even though the E g triplet is inter-band. A similar paring state with attraction in the triplet channel was recently proposed for highly doped systems with only hole pockets [33].…”

Section: Mean Field Phase Diagramsupporting

confidence: 65%

Quasiparticle interference and symmetry of superconducting order parameter in strongly electron-doped iron-based superconductors

et al. 2019

View full text Add to dashboard Cite

Motivated by recent experimental reports of significant spin-orbit coupling (SOC) and a signchanging order-parameter in the Li 1−x Fe x (OHFe) 1−y Zn y Se superconductor with only electron pockets present, we study the possible Cooper-pairing symmetries and their quasiparticle interference (QPI) signatures. We find that each of the resulting states-s-wave, d-wave and helical p-wave-can have a fully gapped density of states consistent with angle-resolved photoemission spectroscopy experiments and, due to SOC, are a mixture of spin singlet and triplet components leading to intraand inter-band features in the QPI signal. Analyzing predicted QPI patterns we find that only the spintriplet dominated even parity A 1g (s-wave) and B 2g (d-wave) pairing states are consistent with the experimental data. Additionally, we show that these states can indeed be realized in a microscopic model with atomic-like interactions and study their possible signatures in spin-resolved STM experiments.2 2 --state to acquire gap nodes, although in principle the nodal area may be very small, proportional to the hybridization ('quasinodes'). On the other hand, ARPES experiments in most of the electron-intercalated materials indicated a nodeless superconducting (sc) state [15,16]. Several proposals for the gap structure have been put forward, including a conventional s ++ -waveThe 2×2 block in equation (11) corresponds to A 1g s-wave pairing. We write J J 13 11 a ¢ = ¢ and find two eigenvalues E J U J J J U U 2 3 16 2 A 11 ¢ = , J J 13 11 ¢ = ¢˜, U 0.1 ¢ = and J 4.6 = . (c) Superconducting gap projected on the inner (blue) and outer (red) Fermi-surface as function of the Fermi angle, zero temperature and at three different values of λ SOC .

show abstract

Section: Mean Field Phase Diagramsupporting

confidence: 65%

Quasiparticle interference and symmetry of superconducting order parameter in strongly electron-doped iron-based superconductors

et al. 2019

View full text Add to dashboard Cite

show abstract

“…In addition to the total mass renormalization, there are significant unexpected differences between these three compounds, even when they have similar doping levels and lattice structures. With respect to superconductivity, the symmetry of the nodal order parameter ( d ‐wave vs. s ‐wave with accidental nodes) is still under debate . It is still unclear which of the five Fermi surfaces sheets plays a dominant role in the superconductivity and which of them are of minor relevance.…”

Section: Afe2as2 a = K Rb Cs Puzzles –A Challenge For Theorymentioning

confidence: 99%

Constraints on the total coupling strengthto bosons in the iron based superconductors

Drechsler

Johnston

Grinenko

et al. 2017

Phys. Status Solidi B

View full text Add to dashboard Cite

Despite the fact that the Fe-based superconductors (FeSCs) were discovered nearly ten years ago, the community is still devoting a tremendous effort towards elucidating their relevant microscopic pairing mechanism(s) and interactions. At present, there is still no consistent interpretation of their normal state properties, where the strength of the electron-electron interaction and the role of correlation effects are under debate. Here, we examine several common materials and illustrate various problems and concepts that are generic for all FeSCs. Based on empirical observations and qualitative insight from density functional theory, we show that the superconducting and low-energy thermodynamic properties of the FeSCs can be described semi-quantitively within multiband Eliashberg theory. We account for an important high-energy mass renormalization phenomenologically, and in agreement with constraints provided by thermodynamic, optical, and angle-resolved photoemission data. When seen in this way, all FeSCs with T c < 40 K studied so far are found to belong to an intermediate coupling regime. This finding is in contrast to the strong coupling scenarios proposed in the early period of the FeSC history. We also discuss several related issues, including the role of band shifts as measured by the positions of van Hove singularities, and the nature of a recently suggested quantum critical point in the strongly hole-doped systems AFe 2 As 2 (A = K, Rb, Cs). Using high-precision full relativistic GGA-band structure calculations, we arrive at a somewhat milder mass renormalization in comparison with previous studies. From the calculated mass anisotropies of all Fermi surface sheets, only the ε-pocket near the corner of the BZ is compatible with the experimentally observed anisotropy of the upper critical field, pointing to its dominant role in the superconductivity of these three compounds.

show abstract

“…1(a)] [3][4][5][6][7], most microscopic theories for iron-based superconductors are focused on the role of spin [8][9][10], orbital [11], or nematic [7,12] fluctuations to the electron pairing and superconductivity. Although angleresolved photoemission spectroscopy (ARPES) experiments on different families of iron-based superconductors have identified the presence of SOC through observation of electronic band splitting at the Brillouin zone center (ZC) below T s [13][14][15], much is unknown concerning the role of SOC to the AF order, nematic phase, electron pairing mechanism, and superconductivity [16][17][18][19].In addition to its impact on the Fermi surface and electronic band dispersions, SOC also brings lattice anisotropies into anisotropies of magnetic fluctuations [20,21] [46][47][48][49][50][51]. Although polarized INS experiments have conclusively established the presence of SOC induced lowenergy spin excitation anisotropy near the resonance mode in different families of iron-based superconductors [23][24][25][26][27][28][29][30][31][32][33][34], the spin excitation anisotropy persists in the paramagnetic tetragonal state, and becomes isotropic at temperatures well above T N and T s [25,…”

mentioning

confidence: 99%

Spin excitation anisotropy in the optimally isovalent-doped superconductor BaFe2(As0.7P0.3)2

Zhang

Yuan

et al. 2017

Phys. Rev. B

View full text Add to dashboard Cite

We use neutron polarization analysis to study spin excitation anisotropy in the optimally isovalent-doped superconductor BaFe 2 (As 0.7 P 0.3 ) 2 (T c = 30 K). Different from optimally hole-and electron-doped BaFe 2 As 2 , where there is a clear spin excitation anisotropy in the paramagnetic tetragonal state well above T c , we find no spin excitation anisotropy for energies above 2 meV in the normal state of BaFe 2 (As 0.7 P 0.3 ) 2 . Upon entering the superconducting state, significant spin excitation anisotropy develops at the antiferromagnetic (AF) zone center Q AF = (1,0,L = odd), while the magnetic spectrum is isotropic at the zone boundary Q = (1,0,L = even). By comparing the temperature, wave vector, and polarization dependence of the spin excitation anisotropy in BaFe 2 (As 0.7 P 0.3 ) 2 and hole-doped Ba 0.67 K 0.33 Fe 2 As 2 (T c = 38 K), we conclude that such anisotropy arises from spin-orbit coupling and is associated with the nearby AF order and superconductivity. DOI: 10.1103/PhysRevB.96.180503 Spin-orbit coupling (SOC) is an interaction of an electron's spin with its motion. While the importance of SOC to the electronic properties of the 4d and 5d correlated electron materials such as Sr 2 RuO 4 and Sr 2 IrO 4 is long recognized [1,2], its relevance to the physics of the 3d correlated electron materials such as iron pnictide superconductors is much less clear. Since iron pnictide superconductors are derived from metallic parent compounds exhibiting antiferromagnetic (AF) order at T N below a tetragonal-to-orthorhombic structural transition temperature T s associated with orbital ordering and nematic phase [ Fig. 1(a)] [3][4][5][6][7], most microscopic theories for iron-based superconductors are focused on the role of spin [8][9][10], orbital [11], or nematic [7,12] fluctuations to the electron pairing and superconductivity. Although angleresolved photoemission spectroscopy (ARPES) experiments on different families of iron-based superconductors have identified the presence of SOC through observation of electronic band splitting at the Brillouin zone center (ZC) below T s [13][14][15], much is unknown concerning the role of SOC to the AF order, nematic phase, electron pairing mechanism, and superconductivity [16][17][18][19].In addition to its impact on the Fermi surface and electronic band dispersions, SOC also brings lattice anisotropies into anisotropies of magnetic fluctuations [20,21] [46][47][48][49][50][51]. Although polarized INS experiments have conclusively established the presence of SOC induced lowenergy spin excitation anisotropy near the resonance mode in different families of iron-based superconductors [23][24][25][26][27][28][29][30][31][32][33][34], the spin excitation anisotropy persists in the paramagnetic tetragonal state, and becomes isotropic at temperatures well above T N and T s [25,26,[30][31][32]. Therefore, it is still unclear how SOC is coupled to spin fluctuation anisotropy and superconductivity.To resolve this problem, we used polarized INS to study low-energy spin ...

show abstract

Hund Interaction, Spin-Orbit Coupling, and the Mechanism of Superconductivity in Strongly Hole-Doped Iron Pnictides

Cited by 75 publications

References 43 publications

Quasiparticle interference and symmetry of superconducting order parameter in strongly electron-doped iron-based superconductors

Quasiparticle interference and symmetry of superconducting order parameter in strongly electron-doped iron-based superconductors

Constraints on the total coupling strengthto bosons in the iron based superconductors

Spin excitation anisotropy in the optimally isovalent-doped superconductor BaFe2(As0.7P0.3)2

Contact Info

Product

Resources

About