Two-gap structure in Yb(Y)Ba2Cu3O7?x single crystals

Aminov, B. A.; Hein, Matthias; Müller, Günter; Piel, H.; Wehler, D.; Ponomarev, Ya. G.; Rosner, K.; Winzer, Klaus

doi:10.1007/bf00724569

Cited by 32 publications

(8 citation statements)

References 11 publications

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“…In this range the effective mass is approximately enclosed between 5 m e and 15 m e leading to the gap energy enclosed between 0.6 to 45 meV. In this range, we have an agreement with experiment data 23,24 which show that the maximum of the gap energy varies between 22 meV and 45 meV and the minimum between 0.5 and 11 meV. For example, if we choice m * /m e = 15, we observe that the gap energy varies between 20 and 45 meV when the Debye energy is enclosed between 0.025 eV and 0.065 eV, and if we choice m * /m e = 10, ∆ varies from 7 meV to 20 meV (Fig.…”

Section: Calculation Of ∆(0)supporting

confidence: 88%

GAP ENERGY, ISOTOPE EFFECT AND COHERENCE LENGTH IN HIGH T_c-OXIDES

Bechlaghem

Mostefa

Zanoun

1999

Int. J. Mod. Phys. B

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The model recently developed by Getino et al. to study the gap energy in the van Hove scenario in high-Tc oxides is extended to study the isotope effect and the coherence length in these materials. We propose a more realistic model by: (1) adding a constant term to the singular logarithmic contribution, within the weak coupling BCS theory and a phonon mediated interaction; (2) assuming the Fermi level lies close to a van Hove singularity for optimal doping. The equations obtained from this approach, are applicable to low as well as high temperature superconductors successfully the superconducting temperature transition Tc, the gap energy ∆, the isotope effect α and the coherence length ξ. For high-Tc oxides, it is found that when the effective mass of carriers tends to be large, α and ξ tend to be small where Tc and ∆ became larges. We shown that when the effective mass of carriers is enclosed between 5 me and 15 me, the values obtained for these parameters are in agreement with experimental data.

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Section: Calculation Of ∆(0)supporting

confidence: 88%

GAP ENERGY, ISOTOPE EFFECT AND COHERENCE LENGTH IN HIGH T_c-OXIDES

Bechlaghem

Mostefa

Zanoun

1999

Int. J. Mod. Phys. B

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“…We will note that two-gap superconductivity was experimentally observed by Ponomarev et al: they found that the dynamic conductance of tunnel break-junctions in single-crystals Y(Yb)BaCuO could not be described using a single gap model, and reproducibly two series of features were demonstrated [98], which was confirmed by theoretical calculations [99,100].…”

Section: The Effect Of Multiple Andreev Reflectionsmentioning

confidence: 57%

“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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“…Oxygen-rich YBCO in superconducting state can absorb almost full spectrum of sunlight due to its very small energy gap ( E g )910, thereby creating electron-hole pairs (e–h). To produce an open circuit voltage V oc by absorption of photons, it is necessary to spatially separate photo-generated e-h pairs before recombination occurs18.…”

Section: Resultsmentioning

confidence: 99%

“…YBa 2 Cu 3 O 7-δ (YBCO) thin films678, in particular, are intensively studied in the form of photovoltaic (PV) cell due to its adjustable energy gap910111213. However, high resistance of the substrate always leads to a low conversion efficiency of the device and masks the primary PV properties of YBCO8.…”

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confidence: 99%

Origin of photovoltaic effect in superconducting YBa2Cu3O6.96 ceramics

Yang

Han

Chang

2015

Sci Rep

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We report remarkable photovoltaic effect in YBa2Cu3O6.96 (YBCO) ceramic between 50 and 300 K induced by blue-laser illumination, which is directly related to the superconductivity of YBCO and the YBCO-metallic electrode interface. There is a polarity reversal for the open circuit voltage Voc and short circuit current Isc when YBCO undergoes a transition from superconducting to resistive state. We show that there exists an electrical potential across the superconductor-normal metal interface, which provides the separation force for the photo-induced electron-hole pairs. This interface potential directs from YBCO to the metal electrode when YBCO is superconducting and switches to the opposite direction when YBCO becomes nonsuperconducting. The origin of the potential may be readily associated with the proximity effect at metal-superconductor interface when YBCO is superconducting and its value is estimated to be ~10–8 mV at 50 K with a laser intensity of 502 mW/cm2. Combination of a p-type material YBCO at normal state with an n-type material Ag-paste forms a quasi-pn junction which is responsible for the photovoltaic behavior of YBCO ceramics at high temperatures. Our findings may pave the way to new applications of photon-electronic devices and shed further light on the proximity effect at the superconductor-metal interface.

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Two-gap structure in Yb(Y)Ba2Cu3O7?x single crystals

Cited by 32 publications

References 11 publications

GAP ENERGY, ISOTOPE EFFECT AND COHERENCE LENGTH IN HIGH T_c-OXIDES

GAP ENERGY, ISOTOPE EFFECT AND COHERENCE LENGTH IN HIGH T_c-OXIDES

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

Origin of photovoltaic effect in superconducting YBa2Cu3O6.96 ceramics

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Two-gap structure in Yb(Y)Ba2Cu3O7?x single crystals

Cited by 32 publications

References 11 publications

GAP ENERGY, ISOTOPE EFFECT AND COHERENCE LENGTH IN HIGH Tc-OXIDES

GAP ENERGY, ISOTOPE EFFECT AND COHERENCE LENGTH IN HIGH Tc-OXIDES

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

Origin of photovoltaic effect in superconducting YBa2Cu3O6.96 ceramics

Contact Info

Product

Resources

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GAP ENERGY, ISOTOPE EFFECT AND COHERENCE LENGTH IN HIGH T_c-OXIDES

GAP ENERGY, ISOTOPE EFFECT AND COHERENCE LENGTH IN HIGH T_c-OXIDES