Raman resonance in iron-based superconductors: The magnetic scenario

Hinojosa, Alberto; Cai, Jiashen; Chubukov, Andrey V.

doi:10.1103/physrevb.93.075106

Cited by 14 publications

(18 citation statements)

References 65 publications

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“…In the SC phase, the QEP acquires coherence and undergoes a metamorphosis into an in-gap collective mode (Fig. 1 B, Inset) similar to several other FeSC superconductors (17,(51)(52)(53)(54). 2) A broad electronic continuum extending beyond 2,000 cm −1 with the intensity peaking at about 450 cm −1 and showing only weak dependence on temperature and doping (the yellow component in Fig.…”

Section: Resultsmentioning

confidence: 52%

Quadrupolar charge dynamics in the nonmagnetic FeSe _{1−
x} S _x superconductors

Zhang

Kasahara

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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We use polarization-resolved electronic Raman spectroscopy to study quadrupolar charge dynamics in a nonmagnetic FeSe1−xSx superconductor. We observe two types of long-wavelength XY symmetry excitations: 1) a low-energy quasi-elastic scattering peak (QEP) and 2) a broad electronic continuum with a maximum at 55 meV. Below the tetragonal-to-orthorhombic structural transition at TS(x), a pseudogap suppression with temperature dependence reminiscent of the nematic order parameter develops in the XY symmetry spectra of the electronic excitation continuum. The QEP exhibits critical enhancement upon cooling toward TS(x). The intensity of the QEP grows with increasing sulfur concentration x and maximizes near critical concentration xcr≈0.16, while the pseudogap size decreases with the suppression of TS(x). We interpret the development of the pseudogap in the quadrupole scattering channel as a manifestation of transition from the non-Fermi liquid regime, dominated by strong Pomeranchuk-like fluctuations giving rise to intense electronic continuum of excitations in the fourfold symmetric high-temperature phase, to the Fermi liquid regime in the broken-symmetry nematic phase where the quadrupole fluctuations are suppressed.

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Section: Resultsmentioning

confidence: 52%

Quadrupolar charge dynamics in the nonmagnetic FeSe _{1−
x} S _x superconductors

Zhang

Kasahara

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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“…One can easily verify that the interactions within a given plaquette involving fermions from different orbitals splits U , J, and J terms into subsets each consisting of three different interactions (there are 5 terms in each subset, like in Eq. (22), but there are only three non-equivalent combunations of different U i , J i and J i .…”

Section: B Interaction Hamiltonianmentioning

confidence: 99%

Magnetism, Superconductivity, and Spontaneous Orbital Order in Iron-Based Superconductors: Which Comes First and Why?

2016

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Magnetism and nematic order are the two nonsuperconducting orders observed in iron-based superconductors. To elucidate the interplay between them and ultimately unveil the pairing mechanism, several models have been investigated. In models with quenched orbital degrees of freedom, magnetic fluctuations promote stripe magnetism, which induces orbital order. In models with quenched spin degrees of freedom, charge fluctuations promote spontaneous orbital order, which induces stripe magnetism. Here, we develop an unbiased approach, in which we treat magnetic and orbital fluctuations on equal footing. Key to our approach is the inclusion of the orbital character of the low-energy electronic states into renormalization group (RG) analysis. We analyze the RG flow of the couplings and argue that the same magnetic fluctuations, which are known to promote s þ− superconductivity, also promote an attraction in the orbital channel, even if the bare orbital interaction is repulsive. We next analyze the RG flow of the susceptibilities and show that, if all Fermi pockets are small, the system first develops a spontaneous orbital order, then s þ− superconductivity, and magnetic order does not develop down to T ¼ 0. We argue that this scenario applies to FeSe. In systems with larger pockets, such as BaFe 2 As 2 and LaFeAsO, we find that the leading instability is either towards a spindensity wave or superconductivity. We argue that in this situation nematic order is caused by composite spin fluctuations and is vestigial to stripe magnetism. Our results provide a unifying description of different ironbased materials.

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“…The composition of the ladder series, however, depends on how we interpret the fundamental diagram in Fig. 20a [157].…”

Section: Ising-nematic Order Vs Orbital Ordermentioning

confidence: 99%

Low-energy microscopic models for iron-based superconductors: a review

2016

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IntroductionThe discovery of a rich family of iron-based superconductors (FeSC) with a variety of different chemical compositions [1,2], such as LaFeAsO (1 1 1 1 material), BaFe 2 As 2 (1 2 2 mat erial), NaFeAs (1 1 1 material), and FeSe (1 1 material), opened a new route to study high-temperature superconductivity. Similarly to high-T c cuprates, which are made of coupled CuO 2 layers, FeSC are also layered systems made of coupled FeAs layers. In both cases, the Cu and Fe atoms form a simple square lattice.The phase diagrams of FeSC are also quite similar to those of the cuprates. Although details of the phase diagrams vary between different families of FeSC, most materials display the key Corresponding Editor Laura Greene AbstractThe development of sensible microscopic models is essential to elucidate the normal-state and superconducting properties of the iron-based superconductors. Because these materials are mostly metallic, a good starting point is an effective low-energy model that captures the electronic states near the Fermi level and their interactions. However, in contrast to cuprates, iron-based high-T c compounds are multi-orbital systems with Hubbard and Hund interactions, resulting in a rather involved 10-orbital lattice model. Here we review different minimal models that have been proposed to unveil the universal features of these systems. We first review minimal models defined solely in the orbital basis, which focus on a particular subspace of orbitals, or solely in the band basis, which rely only on the geometry of the Fermi surface. The former, while providing important qualitative insight into the role of the orbital degrees of freedom, do not distinguish between high-energy and low-energy sectors and, for this reason, generally do not go beyond mean-field. The latter allow one to go beyond mean-field and investigate the interplay between superconducting and magnetic orders as well as Ising-nematic order. However, they cannot capture orbital-dependent features like spontaneous orbital order. We then review recent proposals for a minimal model that operates in the band basis but fully incorporates the orbital composition and symmetries of the lowenergy excitations. We discuss the results of the renormalization group study of such a model, particularly of the interplay between superconductivity, magnetism, and spontaneous orbital order, and compare theoretical predictions with experiments on iron pnictides and chalcogenides. We also discuss the impact of the glide-plane symmetry on the low-energy models, highlighting the key role played by the spin-orbit coupling.

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Raman resonance in iron-based superconductors: The magnetic scenario

Cited by 14 publications

References 65 publications

Quadrupolar charge dynamics in the nonmagnetic FeSe _{1−
x} S _x superconductors

Quadrupolar charge dynamics in the nonmagnetic FeSe _{1−
x} S _x superconductors

Magnetism, Superconductivity, and Spontaneous Orbital Order in Iron-Based Superconductors: Which Comes First and Why?

Low-energy microscopic models for iron-based superconductors: a review

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Raman resonance in iron-based superconductors: The magnetic scenario

Cited by 14 publications

References 65 publications

Quadrupolar charge dynamics in the nonmagnetic FeSe 1− x S x superconductors

Quadrupolar charge dynamics in the nonmagnetic FeSe 1− x S x superconductors

Magnetism, Superconductivity, and Spontaneous Orbital Order in Iron-Based Superconductors: Which Comes First and Why?

Low-energy microscopic models for iron-based superconductors: a review

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Product

Resources

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Quadrupolar charge dynamics in the nonmagnetic FeSe _{1−
x} S _x superconductors

Quadrupolar charge dynamics in the nonmagnetic FeSe _{1−
x} S _x superconductors