Scanning tunneling spectroscopy and break junction spectroscopy on iron-oxypnictide superconductor NdFeAs(O0.9F0.1)

Sugimoto, Akihiro; Ekino, Toshikazu; Ukita, R.; Shohara, Kazuhiro; Okabe, Hirotaka; Akimitsu, Jun; Gabovich, A. M.

doi:10.1016/j.physc.2010.05.038

Cited by 9 publications

(4 citation statements)

References 10 publications

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“…To the best of our knowledge, there are no other data available for Gd-1111 to compare with. Thus, comparing our results for GdO(F)FeAs with the aforementioned data on other 1111-superconductors, we find rather good agreement with 2∆ L /k B T C values determined by "break-junction" technique [36,37] and in some PCAR-measurements [43,44].…”

supporting

confidence: 88%

“…The existence of the large superconducting gap (2∆ L /k B T bulk C > 4) in the 1111-family compounds with critical temperatures 40 K ≤ T C ≤ 53 K was confirmed by tunneling spectroscopy ("break-junction" technique) [36,37], point-contact Andreev reflection (PCAR) spectroscopy of SN-junctions [38,39,40,41,42,43,44], and angle-resolved photoemission spectroscopy (ARPES) [45]. To the best of our knowledge, there are no other data available for Gd-1111 to compare with.…”

mentioning

confidence: 93%

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Study of the Two-Gap Superconductivity in GdO(F)FeAs by ScS-Andreev Spectroscopy

Shanygina,

Ponomarev,

Kuzmichev

et al. 2012

Preprint

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confidence: 88%

mentioning

confidence: 93%

Study of the Two-Gap Superconductivity in GdO(F)FeAs by ScS-Andreev Spectroscopy

Shanygina,

Ponomarev,

Kuzmichev

et al. 2012

Preprint

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“…In our experiments the crystal lattice of the Mg 1−x Al x B 2 samples formally exhibited both insulator and normal metal properties, and SIS and SnS stacks formed on the steps and terraces of the cryogenic clefts due to the layered structure [36,37,[48][49][50][51][52][53][54][55][56][57][58][59][60][61][62]. As such, we got the opportunity to apply four types of spectroscopy to the study of the structure of superconducting order parameters, just as we did with cuprates.…”

Section: Tunneling and Andreev Spectroscopy Of Mg 1−x Al X Bmentioning

confidence: 99%

“Break-junction” technique in application to layered superconductors (Review Article)

Kuzmichev

Kuzmicheva

2016

Low Temperature Physics

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Here presented a systematic study of superconductor-constriction-superconductor contacts realized by a break-junction technique in layered superconductors. Depending on the constriction transparency the tunneling and SnS-Andreev spectroscopies could be used, for the direct determination of values of superconducting gaps, characteristic BCS-ratios and gap temperature dependences in cuprate superconductors, magnesium diboride, novel pnictides and chalcogenides. Basing on these data, one can estimate the gap anisotropy magnitude as well as values of electron-boson coupling constants. We discuss the advantages and difficulties of the break-junction technique and demonstrate this method is powerful enough for high-resolution investigation of optical phonon modes in high-temperature superconducting cuprates and for creating of the contacts with the selective transparence in Mg 1-x Al x B 2 compounds.In memory of Ya. G. Ponomarev, professor, our teacher, warrior, and outstanding experimenter. In memory of S. N. Tchesnokov, mentor, friend, and extraordinary inventor

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“…At the same time, the data for La-1111 polycrystals [36] are in agreement with both, dand s-wave models, while the BCS-ratio is lower: 2Δ/k B T C ~ 3.6 in the s-wave model approximation, and 2Δ/k B T C ~ 4.1 in case of the d-symmetry of the order parameter. Dynamic conductance of the tunnel NIS-contacts (N -normal metal, Ssuperconductor, I -insulator) was studied in a number of works by STM [37][38][39][40][41]. These studies have resolved the only superconducting gap with 2Δ/k B T C = 3.5 ÷ 4.…”

mentioning

confidence: 99%

Andreev spectroscopy of iron-based superconductors: temperature dependence of the order parameters and scaling of $ \Delta_{\rm L, S}$ with $ T_{\rm C}$

Kuzmicheva¹,

Kuzmichev²,

Mikheev³

et al. 2014

Phys.-Usp.

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IntroductionUnexpected discovery in 2006 [1] of the first layered Fe-based high-temperature superconductor (HTSC) -LnOFePn (where Ln -lanthanide, Pn -pnictide; hereafter referred to as "1111") becomes a key issue of modern solid state physics. Since 2008, the class of iron-based superconductors has much expanded: several families of iron pnictides and chalcogenides have been synthesized [2][3][4]. The crystal structure of oxypnictides recalls that of cuprates and is in fact a stack of the superconducting Fe-As layers alternating along the c-direction with spacers, the nonsuperconducting oxide blocks, Ln-O. In spite of the pronounced layered structure and anisotropic physical properties, the electron subsystem in Fe-based superconductors is less quasi-two-dimensional in comparison with that in cuprate HTSC, because the height of the Fe-As blocks exceeds the thickness of the Cu-O planes, whereas the distance between superconducting blocks in iron-based superconductors is significantly less than that in cuprates. The latter seems to be a reason [5] why the critical temperature of Fe-based superconductors, though being as high as T C ≈ 57.5 K [6] still does not reach the cuprate one. Superconductivity in novel materials emerges with the suppression of spin density wave ground state under doping of the superconducting Fe-As layers or under external pressure [7]. The key distinction from cuprates, however, is the multiband nature of newly-discovered superconductivity in iron-based materials. Band structure calculations showed (for a review, see [8]) the coexistence of the electron and the hole quasi-two-dimensional bands in these compounds, whereas the Fermi surfaces consist of slightly warped along the c-direction cylinders (near Γ and M points), where several superconducting condensates could form. Contrary to the observation of the strong isotope effect [9], an early theoretical study showed [10] that the high temperature superconductivity in Fe-based compounds could not to be based on the electron-phonon interaction solely. Although the latter plays an important role, it is incapable [10] to explain the observable values of T C in the framework of the Eliashberg theory [11]. Taking into account the nesting of the Fermi surface sheets along the Γ-M-direction, the vicinity of the antiferromagnetic state [12,13], and the appearance of the experimentally observed [14] peak of dynamic spin susceptibility ("magnetic resonance"), Mazin et al. suggested the theoretical description of the mechanism of superconductivity in iron pnictides and chalcogenides based on sign-changing (in different bands) order parameter -the so-called s ± -model. The simplest initial model considers two isotropic order parameters (in the electron and the hole bands, correspondingly), which have equal amplitudes but are in antiphase (i.e. having opposite signs). The strong interband interaction mediated by spin fluctuations along the Γ-M-direction plays the key role in this model, whereas the intraband electron-phonon coupling is an order of magnit...

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Scanning tunneling spectroscopy and break junction spectroscopy on iron-oxypnictide superconductor NdFeAs(O0.9F0.1)

Cited by 9 publications

References 10 publications

Study of the Two-Gap Superconductivity in GdO(F)FeAs by ScS-Andreev Spectroscopy

Study of the Two-Gap Superconductivity in GdO(F)FeAs by ScS-Andreev Spectroscopy

“Break-junction” technique in application to layered superconductors (Review Article)

Andreev spectroscopy of iron-based superconductors: temperature dependence of the order parameters and scaling of $ \Delta_{\rm L, S}$ with $ T_{\rm C}$

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