Experimental study of the intrinsic multiple Andreev reflections effect in GdO(F)FeAs superconductor array junctions

Kuzmicheva, T. E.; Kuzmichev, S. A.; Mikheev, M. G.; Ponomarev, Ya. G.; Tchesnokov, S. N.; Eltsev, Yu.; Pudalov, V. M.; Pervakov, K. S.; Sadakov, A. V.; Usoltsev, A. S.; Хлыбов, Е. П.; Kulikova, L. F.

doi:10.1209/0295-5075/102/67006

Cited by 36 publications

(64 citation statements)

References 29 publications

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“…therein). The actual number m could be determined when normalize the dI(V )/dV of array to that of single junction [26,28]. Usage of IMARE spectroscopy is preferable since being a direct local probe providing a high accuracy of 2∆/k B T C value [26].…”

Section: Methodsmentioning

confidence: 99%

Direct evidence of two superconducting gaps in FeSe0.5Te0.5: SnS-Andreev spectroscopy and the lower critical field

et al. 2016

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We present direct measurements of the superconducting order parameter in nearly optimal FeSe0.5Te0.5 single crystals with critical temperature TC ≈ 14 K. Using intrinsic multiple Andreev reflection effect (IMARE) spectroscopy and measurements of lower critical field, we directly determined two superconducting gaps, ∆L ≈ 3.3 − 3.4 meV and ∆S ≈ 1 meV, and their temperature dependences. We show that a two-band model fits well the experimental data. The estimated electron-boson coupling constants indicate a strong intraband and a moderate interband interaction.

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Section: Methodsmentioning

confidence: 99%

Direct evidence of two superconducting gaps in FeSe0.5Te0.5: SnS-Andreev spectroscopy and the lower critical field

et al. 2016

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“…Multiple Andreev reflections effect (MARE) spectroscopy is a unique direct probe of the bulk superconducting order parameter [56][57][58]. MARE occurs in ballistic [59] superconductornormal metal-superconductor (SnS) junction which dimension 2a is less than the carrier mean free path l. MARE causes a pronounced excess conductance at low bias voltages (so called "foot"), and a subharmonic gap structure (SGS).…”

Section: Intrinsic Multiple Andreev Reflection Effect (Imare) Spectromentioning

confidence: 99%

“…In order to determine m and the gap(s) value, one should find such natural numbers which scale the I(V) and dI(V)/dV curves for various arrays onto each other, or to achieve the same position of gap features with those for a single-junction spectrum. In array as in a natural structure of the crystal, a contribution of bulk effects well exceeds that of the surface influence [40,57,58].…”

Section: Intrinsic Multiple Andreev Reflection Effect (Imare) Spectromentioning

confidence: 99%

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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“…And by having this interaction as shown by experiments [116,117], both gaps go to zero when a T = T c is the same and when T < T c, one of the gaps is more than the BCS-value and the other is less (Fig. 8) [117] During further development of the theory (I. I. Mazin, [118]) they proposed an alternative mechanism of Cooper pair formation, based on the magnetic resonance of dynamic magnetic susceptibility and then they suggested the interband interaction model for spin and even orbital fluctuations [120].…”

Section: Energy Spectrum Of Superconducting Materials Energy 'Gap' Amentioning

confidence: 85%

High-temperature superconductivity: From macro- to nanoscale structures

Коваленко¹

2016

Nanosystems: Phys. Chem. Math.

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The analysis of achievements, problems and prospects of high-temperature superconductivity (HTSC) in the macro-and nanostructured materials has been given. The main experimental results and theoretical models describing the physical mechanisms of the superconductivity appearance at phenomenological and microscopic levels, including change in the energy spectrum of atoms in these materials with the advent of the 'superconducting' gap at temperatures below the critical transition, as well as the above-critical temperature 'pseudo-gap' have been analyzed.Although the origin of the pseudo-gap is not completely understood, it can be considered as an independent phase transition in the substance prior to the transition to the zero resistance state and insusceptibility (or insensitivity) to external magnetic field in high-temperature superconductors. Features of multi-gap and gapless superconducting materials as well as their ability to further increase the temperature of supercritical transition are discussed. Large resources to create the necessary electron and phonon spectra in the process of high-temperature superconductivity formation are associated with the use of nanoscale structures and nanoparticles of conductors and dielectrics. Electrical conductive contacts between nanoparticles and tunnel chains of nanoclusters, where delocalized electron spectra form similar energy shells to the atomic or nuclear shells, play a significant part here. It is required to further investigate the occurrence of high-temperature superconductivity at the level of interphase layers (non-autonomous phases) in nanostructures containing a large fraction of the substance in this condition. It is essential to develop adequate methods for synthesis of nanoparticles of variable size, structure and morphology, as well as techniques for their consolidation that would ensure the preservation of superconductivity of individual nanoparticles, their chemical, thermal, magnetic and current stability in the dissipative processes with functional and fluctuation effects.

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Experimental study of the intrinsic multiple Andreev reflections effect in GdO(F)FeAs superconductor array junctions

Cited by 36 publications

References 29 publications

Direct evidence of two superconducting gaps in FeSe0.5Te0.5: SnS-Andreev spectroscopy and the lower critical field

Direct evidence of two superconducting gaps in FeSe0.5Te0.5: SnS-Andreev spectroscopy and the lower critical field

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

High-temperature superconductivity: From macro- to nanoscale structures

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