Lower critical field and SNS-Andreev spectroscopy of 122-arsenides: Evidence of nodeless superconducting gap

Abdel-Hafiez, M.; Pereira, Paulo J.; Kuzmichev, S. A.; Kuzmicheva, T. E.; Pudalov, V. M.; Harnagea, Luminita; Kordyuk, A. A.; Silhanek, Alejandro; Moshchalkov, Victor; Shen, Bing; Wen, Hao; Vasiliev, A. N.; Chen, Xiao‐Jia

doi:10.1103/physrevb.90.054524

Cited by 37 publications

(56 citation statements)

References 77 publications

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“…Note that the n=2 doublet located at V2 ≈ ±(3.2-4.4) mV is twice narrower than the first one at V1 ≈ ±(6.5-8.8) mV corresponding to 2L, which is in a well agreement with the SGS formula. Therefore, the large gap is L ≈ 3.2-4.4 meV and has a ~ 30% in-plane anisotropy, similarly to that in the BKFA cited above [68].…”

Section: Intrinsic Multiple Andreev Reflection Effect (Imare) Spectromentioning

confidence: 65%

“…Contemporary The majority of ARPES probes [19,20,22,23] confirm the two gaps with different values as well. [19][20][21][22][23][24]27], lower critical field [32,68], specific heat [30,31], muon-spin-rotation (SR) [23] and optical spectroscopy data [33] . In our studies, the 2L/kBTC determined in optical and Andreev studies are close, while those obtained using Hc1(T) and C(T) are a bit higher, thus favoring the latter; c) the order parameter is possibly anisotropic in both kxky-plane and kz-direction, as discussed e.g.…”

Section: Discussionmentioning

confidence: 99%

“…BKFA, Khasanov et al [7,[19][20][21][22][23][24]27] (triangles), data using C(T), muon-spin-rotation, optical spectroscopy, and lower critical field measurements [30][31][32][33]68] (squares) are shown for comparison.…”

Section: Srmentioning

confidence: 99%

“…. -S arrays [40,51,[56][57][58]68] in a layered sample. The layered single crystal usually exfoliates along the ab-planes with the formation of steps and terraces along the c-direction,…”

Section: Intrinsic Multiple Andreev Reflection Effect (Imare) Spectromentioning

confidence: 99%

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On the structure of the superconducting order parameter in high-temperature Fe-based superconductors

Kuzmicheva¹,

Muratov²,

Kuzmichev³

et al. 2017

Phys.-Usp.

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We discuss the synthesis, characterization, and comprehensive study of Ba-122 single crystals with various substitutions and various superconducting transition temperatures. We use five complementary techniques to obtain a self-consistent set of data on the superconducting properties of Ba-122. A major conclusion of our work is the coexistence of two superconducting condensates differing in the electron–boson coupling strength. The two gaps that develop in distinct Fermi surface sheets are nodeless in the kxky plane and exhibit s-wave symmetry; the two-band model suffices for the description of the main parameters of the superconducting state. A moderate interband coupling and a considerable Coulomb repulsion in the description of the two-gap superconducting state of barium pnictides favor the s++ model.

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Section: Intrinsic Multiple Andreev Reflection Effect (Imare) Spectromentioning

confidence: 65%

Section: Discussionmentioning

confidence: 99%

Section: Srmentioning

confidence: 99%

“…. -S arrays [40,51,[56][57][58]68] in a layered sample. The layered single crystal usually exfoliates along the ab-planes with the formation of steps and terraces along the c-direction,…”

Section: Intrinsic Multiple Andreev Reflection Effect (Imare) Spectromentioning

confidence: 99%

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On the structure of the superconducting order parameter in high-temperature Fe-based superconductors

Kuzmicheva¹,

Muratov²,

Kuzmichev³

et al. 2017

Phys.-Usp.

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“…The H c1 , i.e., the thermodynamic field at which the presence of vortices into the sample becomes energetically favorable, is a very useful parameter, providing key information regarding bulk thermodynamic properties and carrying information about the underlying pairing mechanism. Indeed, the gap properties of different families of pnictides have been investigated by tracking the H c1 and the magnetic penetration depth [24][25][26][27][28][29][30]. The gap properties of these different families display single to double gaps and even the presence of nodes.…”

mentioning

confidence: 99%

Signature of multigap nodeless superconductivity in fluorine-doped NdFeAsO

2017

Self Cite

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We investigate the temperature dependence of the lower critical field Hc1(T ), the field at which vortices penetrate into the sample, of a high-quality fluorine-doped NdFeAsO single crystal under static magnetic fields H parallel to the c-axis. The temperature dependence of the first vortex penetration field has been experimentally obtained and pronounced changes of the Hc1(T) curvature are observed, which is attributed to the multiband superconductivity. Using a two-band model with s-wave-like gaps, the temperature-dependence of the lower critical field Hc1(T ) can be well described. These observations clearly show that the superconducting energy gap in fluorine-doped NdFeAsO is nodeless. The values of the penetration depth at T = 0 K have been determined and confirm that the pnictide superconductors obey an Uemura-style relationship between Tc and λ ab (0) −2 .PACS numbers: 74.20. Rp, 74.25Ha, 74.25.Dw, 74.25.Jb, 74.70.Dd Superconductivity in the iron-pnictide family has been studied intensively due to the comparably large transition temperatures T c of up to 55 K, the unconventional superconducting (SC) properties and interplay with various electronic ground states, such as nematic phase and magnetism [1][2][3][4][5][6]. One of the crucial issues in understanding the SC mechanism in pnictides is the pairing symmetry of the SC gap [7,8]. Although there is a general consensus that spin fluctuations play an important role in the formation of Cooper pairs in pnictides, many aspects such as the role of magnetism, the nature of chemical tuning, and the resultant pairing symmetry remain unsettled [9,10]. Recently, Chubukov and Hirschfeld have shown that there is no general consensus on the nature of pairing in iron-based superconductors leaving the perspectives ranging from s ++ wave, to s ± , and d-wave [11]. It is quite different from that of cuprates in which almost all have a nodal pairing state [12]. Different scenarios have been proposed to explain the mechanism of the superconductivity in pnictides which pointed to the existence of two-gap, isotropic and anisotropic s-wave, d-wave and even p-wave mechanism [13][14][15][16][17][18][19][20][21][22][23]. Such scattered pairing symmetries and various interpretations occur partly due to a sensitive dependence on measurement probes and material quality and stoichiometry.In view of the existing divergence of conclusions about the gap symmetry, there is a clear need to obtain a set of data by comprehensive study. Lower critical field (H c1 ), or equivalently, magnetic penetration depth (λ) is an excellent tool to address this question. The H c1 , i.e., the thermodynamic field at which the presence of vortices into the sample becomes energetically favorable, is a very useful parameter, providing key information regarding bulk thermodynamic properties and carrying information about the underlying pairing mechanism. Indeed, the gap properties of different families of pnictides have been investigated by tracking the H c1 and the magnetic penetration depth [24][25][26]...

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Influence of Multi-orbitals, Coulomb Correlations and Hund’s Coupling on Transition Temperature in Doped Fe-Based Superconductors

Rani

Ajay

2015

J Supercond Nov Magn

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Lower critical field and SNS-Andreev spectroscopy of 122-arsenides: Evidence of nodeless superconducting gap

Cited by 37 publications

References 77 publications

On the structure of the superconducting order parameter in high-temperature Fe-based superconductors

On the structure of the superconducting order parameter in high-temperature Fe-based superconductors

Signature of multigap nodeless superconductivity in fluorine-doped NdFeAsO

Influence of Multi-orbitals, Coulomb Correlations and Hund’s Coupling on Transition Temperature in Doped Fe-Based Superconductors

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