1,721,001 research outputs found
Thermoelectric properties of iron-based superconductors and parent compounds
No full textHerewith, we review the available experimental data of thermoelectric transport properties of iron-based superconductors and parent compounds. We discuss possible physical mechanisms into play in determining the Seebeck effect, from whence one can extract information about Fermi surface reconstruction and Lifshitz transitions, multiband character, coupling of charge carriers with spin excitations and its relevance in the unconventional superconducting pairing mechanism, nematicity, quantum critical fluctuations close to the optimal doping for superconductivity, correlation. Additional information is obtained from the analysis of the Nernst effect, whose enhancement in parent compounds must be related partially to multiband transport and low Fermi level, but mainly to the presence of Dirac cone bands at the Fermi level. In the superconducting compounds, large Nernst effect in the normal state is explained in terms of fluctuating precursors of the spin density wave state, while in the superconducting state it mirrors the usual vortex liquid dissipative regime. A comparison between the phenomenology of thermoelectric behavior of different families of iron-based superconductors and parent compounds allows to evidence the key differences and analogies, thus providing clues on the rich and complex physics of these fascinating unconventional superconductors
Two-dimensional growth of atomically smooth YBCO epitaxial films deposited by PLD in a pulsed oxygen flow
No full textThe employment of superconducting thin films as electronic devices seems to be the most probable future application of these materials. For this application, thin films with extremely smooth surface and very good superconducting as well as structural properties are required.
We deposited YBCO epitaxial thin films by pulsed laser ablation using a pulsed molecular oxygen flow synchronous with the arrival of the ablated species on the substrate.
We studied the dependence of their surface morphology on the deposition pressure and we found an evident improvement in the surface quality by lowering the deposition pressure below 5 x 10(-3) mbar. Films grown in these conditions showed surface roughness lower than 1 Angstrom, transition temperatures above 88 K and critical current densities of about 10(7) A cm(-2) at 4.2 K in self-field
Evidence of the isoelectronic character of F doping in SmFeAsO1−x F x : a first-principles investigation
No full textWe study the electronic structure of the SmFeAsO1−x F x alloy by means of first-principle calculations. We find that, contrary to common believe, F-doping does not change the charge balance between electrons and holes free-carriers in SmFeAsO1−x F x . For energies within a narrow energy range accross , the effect of F-doping on the band structure dispersion is tiny in both the paramagnetic and stripe antiferromagnetic phase. The charge balance between the conducting FeAs-layer and the SmO1−x F x charge reservoir layer is not influenced by the compositional change. The additional charge carried by fluorine, with respect to the oxygen, is compensated by a change in the oxidation state of the Sm ion from 3+ to 2+. A comparison with the SmFe1−x Co x AsO system shows that such charge compensation by the Sm ion is not shared by donors substituting at the Fe site
Effects of electric and magnetic fields on phase-separated La0.7Sr0.3MnO(3-d) thin films
No full textNew artificial superlattices: correlation between structural disorder and transport properties
No full textThe development of thin film deposition techniques allowed the growth of new artificial materials leading to the discovery of new high Te superconducting compounds as infinite layer based superlattices [(BaCuO2)(m)/(CaCuo(2))(n)]). The order of the superlattice structure seems to be one of the crucial parameters to be improved so as to induce a superconductivity onset in these materials and to make them suitable for technological applications.
In this paper we present a study on the correlation between structural disorder and transport properties of several artificial superlattices grown by pulsed laser ablation technique. Our goal was to simulate layered structure of copper oxide superconductors, so as to create new artificial superconducting materials and study charge transfer mechanism. We chose infinite layer phases (SrCuO2, CaCuO2, BaCuO2) for the blocks containing CuO2 planes and doped infinite layer phases (CaCu1-xScxOy, SrCu1-xScxOy, CaCu1-xAgxOy and SrCu1-xAgxOy, with x ranging from 0.1 to 0.2) for the charge reservoir blocks. By means of Reflection High Energy Electron Diffraction (RHEED) and S-rays structural characterization as well as resistivity and Hall effect measurements, we perform a comparative analysis of structural and transport properties of these samples and we tried to explain them in terms of Anderson's theory of disorder
Impact of the 2018 World Para Swimming classification revision on the race results in international Paralympic swimming events
No full textParalympic swimmers compete in classes, according to their swimming functional abilities. The classification protocol of physical and technical tests carried out to assign a class has undergone multiple revisions over time, the latest one in 2018. As a consequence, most of the athletes with physical impairment were required to attend an evaluation session to have their class re-assigned. We monitored the impact of this latest revision on the race results in two international Paralympic swimming events which took place prior to and just after the implementation of the classification revisions. Despite no dramatic changes being observed in the overall class performances and in the within-class performance variability, the race times of athletes that had their class changed were significantly more in trend with the mean times of the new classes than with those of the former classes. However, considering class increments/decrements separately, this was the case only for class increments. Further investigations could clarify this result and possibly provide indications for further improvements in the classification system
Application potential of Fe-based superconductors
No full textIn this paper we report basic properties of iron-based superconductors and review the latest achievements in the fabrication of conductors based on these materials. We compare state-of-the-art results with performances obtained with low-T c and high-T c technical superconductors, evidencing in particular the most significant differences with respect to high-T c cuprate coated conductors. Although the optimization of preparation procedures is yet to be established, a potential range of applications for iron-based superconductors in the high field low temperature regime can be envisaged, where they may become competitors to RE-123 coated conductors
Protocol for the study of self-perceived psychological and emotional well-being of young Paralympic athletes
No full textAbstract Background We present the detailed protocol set up to investigate how agonistic sport affects the self-perceived psychological and emotional well-being of disabled young people. Methods The study will be carried out on a number of subjects as large as 800–1200, using well-established indices that give a quantitative measure of such well-being, namely SF-12 and PGWBI. The related questionnaires will be administered to the participants to a forthcoming international event, the European Para-Youth Games, 9–15 October 2017, Liguria, Italy, as well as to a reference population of a similar number of subjects, made up of young disabled people that do not practice agonistic sport. Discussion We expect that the outcomes of the study may strongly impact not only the socio-sanitary field but also society in general, as disabled people can be considered an extreme situation in the issue of balancing individual needs and environment to pursue psychological well-being. Trial registration ISRCTN14389453 (29 June 2017)
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