Superconducting gap in LiFeAs from three-dimensional spin-fluctuation pairing calculations

Wang, Yeqing; Kreisel, Andreas; Zabolotnyy, V. B.; Борисенко, С. В.; Büchner, B.; Maier, Thomas; Hirschfeld, P. J.; Scalapino, D. J.

doi:10.1103/physrevb.88.174516

Cited by 61 publications

(105 citation statements)

References 42 publications

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“…For small J/U the α − β interaction is repulsive, and its enhancement is expected if antiferromagnetic fluctuations are strong. Not surprisingly, our result for stronger α − β interaction coincides with spin-fluctuation studies of Wang et al 36 and Ummarino et al 39 .…”

Section: Iiii Summary Of Our Resultssupporting

confidence: 92%

“…36 . For the interaction we used the same model as in earlier studies 9 , with Hubbard U and Hund J local interactions in the orbital basis.…”

Section: Iiii Summary Of Our Resultsmentioning

confidence: 99%

“…In our calculations, we set the parameters of the tight-binding model (the elements of the 5×5 matrix) to match the low energy band structure extracted from the ARPES data 36 . The resulting FS's are depicted in Fig.…”

Section: Tight-binding Hamiltonianmentioning

confidence: 99%

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Superconductivity from repulsion in LiFeAs: Novels-wave symmetry and potential time-reversal symmetry breaking

et al. 2014

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We analyze the structure of the pairing interaction and superconducting gap in LiFeAs by decomposing the pairing interaction for various kz cuts into s− and d-wave components and by studying the leading superconducting instabilities. We use the ten orbital tight-binding model, derived from ab-initio LDA calculations with hopping parameters extracted from the fit to ARPES experiments. We find that the pairing interaction almost decouples between two subsets, one consists of the outer hole pocket and two electron pockets, which are quasi-2D and are made largely out of dxy orbital, and the other consists of the two inner hole pockets, which are quasi-3D and are made mostly out of dxz and dyz orbitals. Furthermore, the bare inter-pocket and intra-pocket interactions within each subset are nearly equal. In this situation, small changes in the intra-pocket and inter-pocket interactions due to renormalizations by high-energy fermions give rise to a variety of different gap structures. We focus on s−wave pairing which, as experiments show, is the most likely pairing symmetry in LiFeAs. We find four different configurations of the s−wave gap immediately below Tc: the one in which superconducting gap changes sign between two inner hole pockets and between the outer hole pocket and two electron pockets, the one in which the gap changes sign between two electron pockets and three hole pockets, the one in which the gap on the outer hole pocket differs in sign from the gaps on the other four pockets, and the one in which the gaps on two inner hole pockets have one sign, and the gaps on the outer hole pockets and on electron pockets have different sign. Different s-wave gap configurations emerge depending on whether the renormalized interactions increase attraction within each subset or increase the coupling between particular components of the two subsets. We discuss the phase diagram and experimental probes to determine the structure of the superconducting gap in LiFeAs. We argue that the state with opposite sign of the gaps on the two inner hole pockets has the best overlap with ARPES data. We also argue that at low T , the system may enter into a "mixed" s + is state, in which the phases of the gaps on different pockets differ by less than π and time-reversal symmetry is spontaneously broken.

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Section: Iiii Summary Of Our Resultssupporting

confidence: 92%

“…36 . For the interaction we used the same model as in earlier studies 9 , with Hubbard U and Hund J local interactions in the orbital basis.…”

Section: Iiii Summary Of Our Resultsmentioning

confidence: 99%

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Superconductivity from repulsion in LiFeAs: Novels-wave symmetry and potential time-reversal symmetry breaking

et al. 2014

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“…This agrees with recent ARPES measurements, [27,28] STM quasi-particle interference (QPI), [4] and other theoretical studies. [29] …”

Section: Arxiv:13102455v1 [Cond-matsupr-con] 9 Oct 2013mentioning

confidence: 99%

Impurity states and cooperative magnetic order in Fe-based superconductors

2013

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We study impurity bound states and impurity-induced order in the superconducting state of LiFeAs within a realistic five-band model based on the band structure and impurity potentials obtained from density functional theory (DFT). In agreement with recent experiments, we find that Co impurities are too weak produce sub-gap bound states, whereas stronger impurities like Cu do. We also obtain the bound state spectrum for magnetic impurities, such as Mn, and show how spin-resolved tunnelling may determine the nature of the various defect sites in iron pnictides, a prerequisite for using impurity bound states as a probe of the ground state pairing symmetry. Lastly we show how impurities pin both orbital and magnetic order, providing an explanation for a growing set of experimental evidence for unusual magnetic phases in doped iron pnictides.PACS numbers: 74.70.Xa, 74.62.En, It is crucial to understand the role of disorder in hightemperature superconductors (SC) because the materials are obtained from chemical doping with substitutional impurity atoms. In addition, through the large advance of scanning tunneling microscopy (STM), local perturbations in the host material act as nano-probes of the underlying quantum state. For the Fe-based superconductors (FeSC), a recent series of experiments have measured the local density of states (LDOS) near various impurity sites.[1] In particular, STM measurements within the SC state have focussed largely on FeSe, LiFeAs, and NaFeAs,[2-8] revealing a complex pattern of distinct impurity-induced LDOS modulations including unusual sub-gap bound states, local C 4 symmetry breaking, and generation of electronic dimers. At present no theoretical model exists which correctly captures the LDOS structure near these different impurity sites.Theoretically, both potential and magnetic point-like scatterers can generate in-gap bound states in multi-band s ± -wave SC. The single-impurity problem has been addressed both within simplified two-band models, [9][10][11][12][13][14][15] and a five-band approach, [16] reaching, however, different conclusions about the presence and location of ingap bound states. Recently, an important source of this discrepancy was shown to be the sensitivity of the low-energy states to the band structure and SC gap shape. [17,18] For modelling disorder effects in FeSC, it is therefore crucial to include the correct band structure and minimise the sensitivity of the gap structure by self-consistently calculating the SC gaps arising from this band.A final important recent development is the observation of a component of SDW order observed by e.g. muon spin rotation (µSR) experiments [19][20][21] which "cooperates" with, rather than competes with SC as is commonly assumed. This component, which exists in an intermediate doping range around optimal doping, is evidently correlated with disorder and disappears above T c . This type of disorder-induced magnetism supported by the SC state is reminiscent of that observed in underdoped cuprates where a wedge-like extension...

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“…Further the lack of nesting between hole at the Γ point and electron pockets at the M point is not favorable to magnetic interaction. Nevertheless Wang et al [52] were able to show, through a detail analysis of the pairing vertex, that spin fluctuation pairing can still be the operative mechanism in this material. We also find no evidence that our peak in I 2 χ(ω) at ∼ 8 meV is significantly depleted as the normal state is approach with increasing temperature.…”

Section: Inclusion Of Anisotropic Gapmentioning

confidence: 99%

Electron-boson spectral density of LiFeAs obtained from optical data

Hwang

Ćarbotte

Min

et al. 2015

J. Phys.: Condens. Matter

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Abstract. We analyze existing optical data in the superconducting state of LiFeAs at T = 4 K, to recover its electron-boson spectral density. A maximum entropy technique is employed to extract the spectral density I 2 χ(ω) from the optical scattering rate. Care is taken to properly account for elastic impurity scattering which can importantly affect the optics in an s-wave superconductor, but does not eliminate the boson structure. We find a robust peak in I 2 χ(ω) centered about Ω R ∼ = 8.0 meV or 5.3 k B T c (with T c = 17.6 K). Its position in energy agrees well with a similar structure seen in scanning tunneling spectroscopy (STS). There is also a peak in the inelastic neutron scattering (INS) data at this same energy. This peak is found to persist in the normal state at T = 23 K. There is evidence that the superconducting gap is anisotropic as was also found in low temperature angular resolved photoemission (ARPES) data.

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Superconducting gap in LiFeAs from three-dimensional spin-fluctuation pairing calculations

Cited by 61 publications

References 42 publications

Superconductivity from repulsion in LiFeAs: Novels-wave symmetry and potential time-reversal symmetry breaking

Superconductivity from repulsion in LiFeAs: Novels-wave symmetry and potential time-reversal symmetry breaking

Impurity states and cooperative magnetic order in Fe-based superconductors

Electron-boson spectral density of LiFeAs obtained from optical data

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