Orbital resonance mode in superconducting iron pnictides

Lee, Wei Cheng; Phillips, Philip

doi:10.1209/0295-5075/103/57003

Cited by 7 publications

(4 citation statements)

References 45 publications

(57 reference statements)

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“…The immediate consequence of attraction in the B 2g channel is the ingap resonant modes below the quasi-particle continuum in the superconducting state. Hence the attraction in the XY channel leads to a sharp resonance below the p-h continuum 110 . We note that the attraction causing the resonance is operational in the p-h channel, while it is well known that the p-h and Cooper channel do not have a separate existence and are combined into a single ingap mode 101 .…”

Section: A Particle-hole Exciton Modesmentioning

confidence: 99%

Critical quadrupole fluctuations and collective modes in iron pnictide superconductors

et al. 2016

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The multiband nature of iron pnictides gives rise to a rich temperature-doping phase diagram of competing orders and a plethora of collective phenomena. At low dopings, the tetragonal-to-orthorhombic structural transition is closely followed by a spin density wave transition both being in close proximity to the superconducting phase. A key question is the nature of high-Tc superconductivity and its relation to orbital ordering and magnetism. Here we study the NaFe1−xCoxAs superconductor using polarization-resolved Raman spectroscopy. The Raman susceptibility displays critical enhancement of non-symmetric charge fluctuations across the entire phase diagram which are precursors to a d-wave Pomeranchuk instability at temperature θ(x). The charge fluctuations are interpreted in terms of quadrupole inter-orbital excitations in which the electron and hole Fermi surfaces breathe in-phase. Below Tc, the critical fluctuations acquire coherence and undergo a metamorphosis into a coherent ingap mode of extraordinary strength.

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Section: A Particle-hole Exciton Modesmentioning

confidence: 99%

Critical quadrupole fluctuations and collective modes in iron pnictide superconductors

et al. 2016

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“…Fingerprints of its presence have been reported in the Raman spectra of optimally hole doped K-Ba122 where several sharp modes are detected below T c [181,182]. In principle both the nematic resonance and the BS mode can be simultaneously present in the SC Raman spectrum and may even couple [183,184]. However it is likely that their respective visibility will be strongly system dependent.…”

Section: Relationship With Other Superconducting Collective Modesmentioning

confidence: 99%

Charge nematicity and electronic Raman scattering in iron-based superconductors

Gallais

Paul

2015

Comptes Rendus. Physique

127

170

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We review the recent developments in electronic Raman scattering measurements of charge nematic fluctuations in iron-based superconductors. A simple theoretical framework of a d-wave Pomeranchuk transition is proposed in order to capture the salient features of the spectra. We discuss the available Raman data in the normal state of 122 iron-based systems, particularly Co doped BaFe2As2, and we show that the low energy quasi-elastic peak, the extracted nematic susceptibility and the scattering rates are consistent with an electronic driven structural phase transition. In the superconducting state with a full gap the quasi-elastic peak transforms into a finite frequency nematic resonance, evidences for which are particularly strong in the electron doped systems. A crucial feature of the analysis is the fact that the electronic Raman signal is unaffected by the acoustic phonons. This makes Raman spectroscopy a unique probe of electronic nematicity.

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“…Secondly, our calculation shows that the two large peaks observed in the B 2g geometry originate from both electron and hole pockets. The existence of either the Bardasis-Schrieffer [13] or orbital resonance [28] modes suggested in the previous studies, is not necessary. Finally, the previous conclusion in [13] about the existence of the large gap anisotropy on the δ (outer) electron pocket in the hole doped 122 case is not reliable.…”

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confidence: 83%

Superconducting gaps via Raman scattering in iron superconductors

Setty

2014

Phys. Rev. B

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We investigate non-resonant Raman response for iron-based superconductors using the framework of an effective S4 model that was recently proposed to capture the essential electronic and magnetic properties of Iron based superconductors. We compute the momentum matrix elements and the resulting Raman vertices exactly for different polarization geometries and amazingly find that a simple coskxcosky superconducting gap function is in good agreement with experimental data measured in both iron-pnictides and iron-chalcogenides. The Raman peaks are also matched quantitatively with the measured superconducting gaps by other experimental techniques. The result strengthens the validity of the S4 model and the dominance of the s-wave pairing for iron-based superconductors.The discovery of Iron based superconductors [1,2] has inspired continued searches for new ways of understanding the mechanism of superconductivity. The major difficulty in understanding their electronic structure is the occurrence of multiple bands at the Fermi level. Although many effective model Hamiltoniansconstructed by including different number of orbitals like two [3], three [4] and five [5] orbitals -have been proposed, their successes are limited; that is, while simple two and three orbital models leave out several essential features observed in experiments, five orbital models lack analytical and numerical tractability which makes it hard for theoretical calculations to predict meaningful results and therefore, fail to isolate the vital ingredients which control the diverse and interesting phenomena observed in experiments.Recently it was suggested that the underlying, low energy, electronic structure in the iron based superconductors was governed by an S 4 symmetric, two weakly coupled, single orbital models [6]. The motivation for such a model, henceforth referred to as the S 4 model, was derived from the fact that if the hopping parameters in the original five band model [5] are tranformed to a different gauge setting, then, one can use the effective d xz and d yz orbitals to construct a model that accurately describes the essential band structure near Fermi levels. In the real space picture, the two orbitals can be naturally segmented into two groups : one, coupled to the As atoms on the top of the F e layer and the other, to those at the bottom, with each group containing contributions from both the sub-lattices. It was also demonstrated that the gauge transformation maps the s−wave pairing symmetry in the original one F e Brillouin Zone (BZ) to the d− wave pairing symmetry in the folded BZ defined on the two sublattices, thus establishing that the relevant symmetry which unifies the different families of high T c superconductors is a combination of both the hopping and the pairing symmetries. It remains, now, to compute the consequences and predictions of such a model, examine its accuracy, and determine its suitability in describing the observed experimental phenomena. It is important to note that the critical difference between the S 4 ...

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Orbital resonance mode in superconducting iron pnictides

Cited by 7 publications

References 45 publications

Critical quadrupole fluctuations and collective modes in iron pnictide superconductors

Critical quadrupole fluctuations and collective modes in iron pnictide superconductors

Charge nematicity and electronic Raman scattering in iron-based superconductors

Superconducting gaps via Raman scattering in iron superconductors

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