Nodal superconducting gap in tetragonal FeS

Xing, Jie; Lin, Hai; Li, Yufeng; Sheng, L.; Zhu, Xiyu; Yang, Huan; Wen, Hao

doi:10.1103/physrevb.93.104520

Cited by 42 publications

(52 citation statements)

References 38 publications

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“…However, the incoherent spectral weight of γ might still contribute to the zero-energy excitations at low temperatures. This could explain the nodal-gap-like behavior observed in thermal conductivity and specific heat measurements [20,21]. On the other hand, because the incoherent γ band would not contribute to the superfluid response, if the superconducting gaps in the other bands are nodeless, µSR could still observe an overall nodeless-gap behavior for FeS [18,19].…”

Section: Discussionmentioning

confidence: 94%

“…Muon spin rotation (µSR) measurements favor the fully-gapped superconductivity coexisting with a low-moment magnetic state at low temperature in polycrystalline FeS [18,19]. On the contrary, thermal conductivity and specific heat measurements support the existence of a nodal gap [20,21], while scanning tunneling spectroscopy indicates a highly anisotropic or nodal superconducting gap structure [22]. Furthermore, a theoretical calculation predicted d x 2 −y 2 pairing symmetry in FeS [23].…”

Section: Introductionmentioning

confidence: 99%

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Electronic structure of FeS

Miao

Niu

et al. 2017

Phys. Rev. B

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Here we report the electronic structure of FeS, a recently identified iron-based superconductor. Our high-resolution angle-resolved photoemission spectroscopy studies show two hole-like (α and β) and two electron-like (η and δ) Fermi pockets around the Brillouin zone center and corner, respectively, all of which exhibit moderate dispersion along kz. However, a third hole-like band (γ) is not observed, which is expected around the zone center from band calculations and is common in iron-based superconductors. Since this band has the highest renormalization factor and is known to be the most vulnerable to defects, its absence in our data is likely due to defect scattering -and yet superconductivity can exist without coherent quasiparticles in the γ band. This may help resolve the current controversy on the superconducting gap structure of FeS. Moreover, by comparing the β bandwidths of various iron chalcogenides, including FeS, FeSe1−xSx, FeSe, and FeSe1−xTex, we find that the β bandwidth of FeS is the broadest. However, the band renormalization factor of FeS is still quite large, when compared with the band calculations, which indicates sizable electron correlations. This explains why the unconventional superconductivity can persist over such a broad range of isovalent substitution in FeSe1−xTex and FeSe1−xSx.

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Section: Discussionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Electronic structure of FeS

Miao

Niu

et al. 2017

Phys. Rev. B

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“…To evaluate the right-hand side of the relation, we use the Sommerfeld coefficient of γ = 5.73 mJ/(mol K 2 ) [34] and T c = 9.1 K for FeSe [20]. For FeS, γ = 3.8 mJ/(mol K 2 ) [6]. Because T c for FeSe was determined with a zero-resistance criterion in [20], we use a similarly determined T c of 3.9 K for FeS for the comparison.…”

Section: Methodsmentioning

confidence: 99%

Upper critical field and quantum oscillations in tetragonal superconducting FeS

et al. 2016

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The magnetoresistance and magnetic torque of FeS are measured in magnetic fields B of up to 18 T down to a temperature of 0.03 K. The superconducting transition temperature is found to be Tc = 4.1 K, and the anisotropy ratio of the upper critical field Bc2 at Tc is estimated from the initial slopes to be Γ(Tc) = 6.9. Bc2(0) is estimated to be 2.2 and 0.36 T for B ab and c, respectively. Quantum oscillations are observed in both the resistance and torque. Two frequencies F = 0.15 and 0.20 kT are resolved and assigned to a quasi-two-dimensional Fermi surface cylinder. The carrier density and Sommerfeld coefficient associated with this cylinder are estimated to be 5.8 × 10−3 carriers/Fe and 0.48 mJ/(K 2 mol), respectively. Other Fermi surface pockets still remain to be found. Band-structure calculations are performed and compared to the experimental results.

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“…This conclusion contrasts with some other studies of tFeS, which have found evidence for nodes in the gap function. 30,31 However, a previous µSR study has also reported fully-gapped behaviour, though the best fit was for two s-wave gaps.…”

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confidence: 93%

Robustness of superconductivity to competing magnetic phases in tetragonal FeS

et al. 2016

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We have determined the superconducting and magnetic properties of a hydrothermally synthesized powder sample of tetragonal FeS using muon spin rotation (µSR). The superconducting properties are entirely consistent with those of a recently published study, showing fully gapped behavior and giving a penetration depth of λ ab = 204(3) nm. However, our zero-field µSR data are rather different and indicate the presence of a small, non-superconducting magnetic phase within the sample. These results highlight that sample-to-sample variations in magnetism can arise in hydrothermally prepared phases, but interestingly the superconducting behavior is remarkably insensitive to these variations.

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Nodal superconducting gap in tetragonal FeS

Cited by 42 publications

References 38 publications

Electronic structure of FeS

Electronic structure of FeS

Upper critical field and quantum oscillations in tetragonal superconducting FeS

Robustness of superconductivity to competing magnetic phases in tetragonal FeS

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