Neutron Spin Resonance in a Quasi-Two-Dimensional Iron-Based Superconductor

Hong, Wenshan; Song, Lingnan; Liu, Bo; Li, Zezong; Zeng, Zhenyuan; Li, Yang; Wu, Dong; Xie, Tao; Danilkin, Sergey; Ghosh, Haranath; Ghosh, Abyay; Hu, Jiangping; Zhao, Lin; Zhou, Xianju; Qiu, Xianggang; Li, Shiliang; Luo, Huiqian

doi:10.1103/physrevlett.125.117002

Cited by 44 publications

(48 citation statements)

References 78 publications

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“…Conversely, no nodal gaps were observed by heat transport [17] and optical spectroscopy [18] in Cs-12442 samples, and by ARPES [9], lower critical field measurements [19] and tunneling spectroscopy (STS) [20] in K-12442 single crystals. STS measurements revealed a single (contrasting all other reports) s-wave gap, with an intraband coupling mechanism that would be incompatible with spin-fluctuation-mediated superconductivity, for which clear signatures were observed by neutron spin resonance measurements [21,22]. This large set of contrasting reports highlights the complexity of these systems, and the need of joint investigations of the same high-quality samples by means of different techniques in order to shed light on this complicated matter.…”

Section: Introductionmentioning

confidence: 71%

Nodal multigap superconductivity in the anisotropic iron-based compound RbCa2Fe4As4F2

et al. 2022

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The 12442 compounds are a recently discovered family of iron-based superconductors, that share several features with the cuprates due to their strongly anisotropic structure, but are so far poorly understood. Here, we report on the gap structure and anisotropy of RbCa2(Fe1−xNix)4As4F2 single crystals, investigated by a combination of directional point-contact Andreev-reflection spectroscopy and coplanar waveguide resonator measurements. Two gaps were identified, with clear signatures of d-wave-like nodal structures which persist upon Ni doping, well described by a two-band d − d state with symmetry-imposed nodes. A large London penetration depth anisotropy was revealed, weakly dependent on temperature and fully compatible with the d − d model.

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Section: Introductionmentioning

confidence: 71%

Nodal multigap superconductivity in the anisotropic iron-based compound RbCa2Fe4As4F2

et al. 2022

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“…KCa 2 Fe 4 As 4 F 2 is the first and a well-studied 12442-type IBS [8] and its anisotropic physical properties have been demonstrated. In KCa 2 Fe 4 As 4 F 2 , quasi two-dimensional electronic behavior, which is similar to that of cuprate superconductors, has been revealed by neutron spin resonance [15]. The quasi two-dimensional electronic state was also suggested from the large anisotropy of electrical resistivity, with ρ c /ρ ab > 100, and semiconductor-like ρ c [16].…”

Section: Introductionmentioning

confidence: 83%

Critical Current Density and Vortex Dynamics in Pristine and Irradiated KCa2Fe4As4F2

et al. 2021

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We report the critical current density (Jc) and vortex pinning properties in single crystals of a novel iron-based superconductor (IBS) KCa2Fe4As4F2 with large Jc in the pristine state, before and after introduction of artificial defects by swift-particle irradiation. The effects of 2.6 GeV U and 3 MeV proton irradiations in KCa2Fe4As4F2 single crystals on transition temperature Tc and Jc, including its dose dependence, are systematically studied. Jc~8 MA/cm2 under a self-field at 2 K in the pristine crystal is strongly enhanced up to 19.4 and 17.5 MA/cm2 by irradiation of 2.6 GeV U-ions and 3 MeV protons, respectively. Suppression of Tc and dose dependence of Jc in KCa2Fe4As4F2 is different from that in a representative IBS of (Ba,K)Fe2As2, which can be explained by considering the presence of embedded defects in pristine KCa2Fe4As4F2. The vortex dynamics in the pristine and proton irradiated KCa2Fe4As4F2 single crystals are also investigated from the analyses of the field dependence of Jc and the normalized magnetic relaxation rate. In addition to the contribution of embedded defects, weak collective pinning is considered for comprehensive analyses. Vortex dynamics in KCa2Fe4As4F2 is similar to those in (Ba,K)Fe2As2 to some extent, and different from that in anisotropic Li0.8Fe0.2OHFeSe. Large anisotropy, due to the presence of insulating blocking layers in KCa2Fe4As4F2, which leads to much lower irreversibility field (Hirr) compared with 122-type IBSs, strongly affect the vortex dynamics.

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“…Angle-resolved photoemission (ARPES) measurements on KCa 2 Fe 4 As 4 F 2 (K12442) have observed bilayer band splitting [10] analogous to that in Bi 2 Sr 2 CaCu 2 O 8+δ [22,23]. An inelastic neutron scattering study has revealed a 2D spin resonant mode with downward dispersion in K12442 [8], also resembling the behavior in cuprates.…”

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confidence: 99%

“…The recently discovered 12442-type Fe-based superconductors (FeSCs) ACa 2 Fe 4 As 4 F 2 (A = K, Rb, or Cs) with a T c ≃ 28-33.5 K have attracted considerable attention [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. These compounds consist of double Fe 2 As 2 layers separated by insulating Ca 2 F 2 layers, resulting in a quasi-two-dimensional (quasi-2D) layered structure with a resistivity anisotropy of ρ c (T )/ρ ab (T ) ∼ 10 3 at low temperatures [4,5], which is significantly larger than that of FeSe (∼3-4) [16], LiFeAs (∼1-3) [17] and the BaFe 2 As 2 family (∼2-6) [18,19], but comparable to that of the high-T c cuprates [20,21].…”

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confidence: 99%

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Pseudogap and Strong Pairing Induced by Incipient and Shallow Bands in the Quasi-Two-Dimensional KCa$_{2}$Fe$_{4}$As$_{4}$F$_{2}$

Hao,

Hong,

Zhou

et al. 2021

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The optical properties of KCa2Fe4As4F2 (K12442, Tc = 33.5 K) and KCa2(Fe0.95Ni0.05)4As4F2 (Ni-K12442, Tc = 29 K) have been examined at a large number of temperatures. For both samples, a nodeless superconducting gap is clearly observed in the optical conductivity at 5 K. The superconducting gap ∆ ≃ 8.7 meV (2∆/kBTc ≃ 6.03) in K12442, pointing towards strong-coupling Cooper pairs, but in sharp contrast, ∆ ≃ 4.6 meV (2∆/kBTc ≃ 3.68) in Ni-K12442, which agrees with the BCS weak-coupling pairing state. More intriguingly, below T * ≃ 75 K, the optical conductivity of K12442 reveals a pseudogap that smoothly evolves into the superconducting gap below Tc, while no such behavior is detected in the electron-doped Ni-K12442. The comparison between the two samples hints that the pseudogap and strong-coupling Cooper pairs in K12442 may be intimately related to the shallow and incipient bands.

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Neutron Spin Resonance in a Quasi-Two-Dimensional Iron-Based Superconductor

Cited by 44 publications

References 78 publications

Nodal multigap superconductivity in the anisotropic iron-based compound RbCa2Fe4As4F2

Nodal multigap superconductivity in the anisotropic iron-based compound RbCa2Fe4As4F2

Critical Current Density and Vortex Dynamics in Pristine and Irradiated KCa2Fe4As4F2

Pseudogap and Strong Pairing Induced by Incipient and Shallow Bands in the Quasi-Two-Dimensional KCa$_{2}$Fe$_{4}$As$_{4}$F$_{2}$

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