Evaluation of superconducting gaps in optimally doped Ba(Fe1−Co )2As2/Fe bilayers by ultrafast time-resolved spectroscopy

Bonavolontà, C.; Lisio, C. de; Valentino, M.; Parlato, L.; Pèpe, G.; Kurth, Felix; Iida, K.

doi:10.1016/j.physc.2014.04.013

Cited by 4 publications

(5 citation statements)

References 31 publications

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“…On the other hand, the superconducting gap Δ 0 estimated for Ba-122/Fe is larger compared to the sample without the Fe buffer layer, which implies that the Fe buffer layer affects the Fermi surface without destroying superconductivity. It is worth mentioning that a complete transient reflectivity data analysis concerning the Ba-122/Fe superconducting samples evidenced the presence of two gaps, as reported elsewhere [15].…”

Section: Resultssupporting

confidence: 75%

“…In IBS, ultrafast spectroscopy has been used to reveal the existence of pseudogap states [8], competition between SDWs and superconducting states [13] and to understand the role of interband interactions and gap symmetry [14]. Moreover, this technique ultrafast spectroscopy has been used to investigate quasiparticle (QP) dynamics in Ba-122 family, proving its ability to reveal the multigap nature of such superconductors [15].…”

Section: Introductionmentioning

confidence: 99%

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Influence of Fe Buffer Layer on Co-Doped BaFe₂As₂Superconducting Thin Films

Bonavolontà

Lisio

Valentino

et al. 2015

Advances in Condensed Matter Physics

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A systematic characterization of Co-doped BaFe2As2(Ba-122) thin films has been carried out. Two samples were available, one grown on CaF2substrate and the other on MgO with an Fe buffer layer. The goal was to investigate films’ magnetic and superconducting properties, their reciprocal interplay, and the role played by the Fe buffer layer in modifying them. Morphological characterization and Energy Dispersive X-ray analyses on the Fe-buffered sample demonstrate the presence of diffused Fe close to the Co-doped Ba-122 outer surface as well as irregular holes in the overlying superconducting film. These results account for hysteresis loops obtained with magneto-optic Kerr effect measurements and observed at both room and low temperatures. The magnetic pattern was visualized by magneto-optical imaging with an indicator film. Moreover, we investigated the onset of superconductivity through a measure of the superconducting energy gap. The latter is strictly related to the decay time of the excitation produced by an ultrashort laser pulse and has been determined in a pump-probe transient reflectivity experiment. A comparison of results relative to Co-doped Ba-122 thin films with and without Fe buffer layer is finally reported.

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Section: Resultssupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Influence of Fe Buffer Layer on Co-Doped BaFe₂As₂Superconducting Thin Films

Bonavolontà

Lisio

Valentino

et al. 2015

Advances in Condensed Matter Physics

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“…3 (right) is the average of 10 acquisitions. Further experimental details can be found in refs 19 , 20 and 21 .…”

Section: Methodsmentioning

confidence: 99%

Anomalous evolution of broadband optical absorption reveals dynamic solid state reorganization during eumelanin build-up in thin films

Bonavolontà

Lisio

d’Ischia

et al. 2017

Sci Rep

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The origin of eumelanin optical properties remains a formidable conundrum preventing a detailed understanding of the complex photo-protective role of these widespread natural pigments and the rational design of innovative bioinspired materials for optoelectronic applications. Here we report the unusual kinetic and thickness-dependent evolution of the optical properties of black eumelanin polymers generated by spontaneous aerial polymerization of 5,6-dihydroxyindole (DHI) thin films (0.1–1 μm), consistent with peculiar solid state reorganization mechanisms governing broadband absorption. The complete reversal of eumelanin UV-visible transmittance spectrum curvature on passing from 0.2 to 0.5 μm thick films, the marked increase in visible extinction coefficients with increasing film thickness and the higher UV extinction coefficients in slowly vs. rapidly generated polymers concur to support distinct dynamic regimes of solid-state molecular reorganization at the nanoscale level and to do affect the development of broadband visible absorption. Solid state control of molecular reorganization disclosed herein may delineate new rational strategies for tuning optical properties in eumelanin thin films for optoelectronic applications.

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“…Guided by the idea that defects not only affect the spectrum of excitations of the pristine system, but they can even induce/foster new excitations in the system in connection to their degree of positional disorder, we have performed time-resolved reflectivity (TRR) pump-probe experiments on three films of N d 1.83 Ce 0.17 CuO 4±δ with substantially different in-plane transport properties induced by different fabrication procedures and/or ex-situ thermal treatments with respect to oxygen content and disorder. Our choice of the TRR technique was dictated by the well-proven capability of pump-probe techniques to reveal the presence of various kinds of excitations in a system identifying their different relaxation dynamics [23][24][25][26][27][28][29][30][31][32][33][34] . A new excitation manifested as additional relaxation channel proving that it is possible to turn a TRR measurement, although indirectly, into a disorder-sensitive probe.…”

Section: Introductionmentioning

confidence: 99%

Disorder-sensitive pump-probe measurements onNd1.83Ce0.17CuO4±δfilms

et al. 2016

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We find an unambiguous relationship between disorder-driven features in the temperature dependence of the resistance and the behavior, as functions of the temperature, of the parameters necessary to describe some of the relaxation processes in the photoinduced differential time-resolved reflectivity of three samples of N d1.83Ce0.17CuO 4±δ . The latter, sharing the same Ce content, have been fabricated and annealed ad-hoc in order to differ only for the degree of disorder, mainly related to oxygen content and location, and, consequently, for the temperature dependence of the resistance: two of them present a minimum in the resistance and behave as a superconductor and as a metal, respectively, the third behaves as an insulator. The systematic coherence between the resistance and the relaxation parameters behaviors in temperature for all three samples is absolutely remarkable and shows that pump-probe measurements can be extremely sensitive to disorder as it drives the emergence of new excitations and of the related relaxation channels as in this paradigmatic case.

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Evaluation of superconducting gaps in optimally doped Ba(Fe1−Co )2As2/Fe bilayers by ultrafast time-resolved spectroscopy

Cited by 4 publications

References 31 publications

Influence of Fe Buffer Layer on Co-Doped BaFe₂As₂Superconducting Thin Films

Influence of Fe Buffer Layer on Co-Doped BaFe₂As₂Superconducting Thin Films

Anomalous evolution of broadband optical absorption reveals dynamic solid state reorganization during eumelanin build-up in thin films

Disorder-sensitive pump-probe measurements onNd1.83Ce0.17CuO4±δfilms

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Evaluation of superconducting gaps in optimally doped Ba(Fe1−Co )2As2/Fe bilayers by ultrafast time-resolved spectroscopy

Cited by 4 publications

References 31 publications

Influence of Fe Buffer Layer on Co-Doped BaFe2As2Superconducting Thin Films

Influence of Fe Buffer Layer on Co-Doped BaFe2As2Superconducting Thin Films

Anomalous evolution of broadband optical absorption reveals dynamic solid state reorganization during eumelanin build-up in thin films

Disorder-sensitive pump-probe measurements onNd1.83Ce0.17CuO4±δfilms

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Influence of Fe Buffer Layer on Co-Doped BaFe₂As₂Superconducting Thin Films

Influence of Fe Buffer Layer on Co-Doped BaFe₂As₂Superconducting Thin Films