The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In the present paper we report a summary of the infrared studies on the multi-band Ba(Fe1-xCox)2As2 pnictide system, devoted to the detection of superconducting gaps in the terahertz region. Generally, results obtained in the superconducting state indicate the presence of two gaps, but univocal results have not been obtained so far. We show that all the literature gap values of the Ba(Fe1-xCox)2As...
Multi-gap superconductors exhibit interesting properties. In an N-gap superconductor, we have in general U(1)N phase invariance. This multiple-phase invariance is partially or totally spontaneously broken in a superconductor. The Nambu-Goldstone modes, as well as Higgs modes, are important and will play an important role in multi-condensate superconductors. The additional phase invariance leads to...
We report a detailed study on control of sputtering parameters for synthesizing NbN superconducting thick films. The NbN films are deposited on single crystalline silicon (100) by DC reactive sputtering, i.e., deposition of Nb in the presence of reactive N2 gas. After several runs, samples were prepared with Ar:N2 partial gas ratios of 90:10, 80:20 and 70:30 for a deposition time of 10 minutes. The...
A large number of compounds which contain BiS2 layers exhibit enhanced superconductivity upon electron doping. Much interest and research effort has been focused on BiS2-based compounds which provide new opportunities for exploring the nature of superconductivity. Important to the study of BiS2-based superconductors is the relation between structure and superconductivity. By modifying either the superconducting...
Bi4O4S3 was the first superconductor discovered in the BiS2 family of novel superconductors. The subfamily of Bi-O-S systems now expanded andwas probed both theoretically and experimentally. Here we review the experimentalwork done on the Bi-O-S compounds, and compare it with theoretical results obtained using ab-initio methods. In particular we calculate the charge carrier density using an ab-initio...
We review theoretical aspects of the studies on the recently discovered BiCh2 (Ch=chalcogen) based superconductors. We first focus on the electronic band structure, the Fermi surface and their correlation with the lattice structure. We then discuss the phonon features and the issue of the lattice instability. Finally, we survey the phonon-mediated as well as the unconventional pairing mechanisms that...
Inhomogeneity and phase separation in unconventional superconducting materials is a topic of increasing interest, as the competition between phases with different types of ordering is thought to play an important role in the emergence of the high temperature superconducting state. A wide range of experimental techniques are available for investigating the crystallography of these complex materials,...
Since the discovery of high temperature superconductivity in iron pnictides in 2008, many iron-based superconductors (IBSs) with various crystal structures have been exploited.Among them, superconductivity with the onset transition temperature Tc up to 49 K has been detected in rare earth element doped CaFe2As2 system (CaRE122). The electron doping induced high Tc values clearly exceed the highest...
High temperature superconductivity in K-doped 1,2:8,9-dibenzenopentacene (C30H18) has been recently reported [1] with Tc = 33 K, the highest among organic superconductors at ambient pressure. Here we report on our search for superconductivity in K, Ba, and Ca-doped hydrocarbon organic materials. We find that Ba-anthracene (C14H10) and K-Picene (C22H14) show features characteristics of superconducting...
Emerets’s experiments on pressurized sulfur hydride have shown that H3S metal has the highest known superconducting critical temperature Tc = 203 K. The Emerets data show pressure induced changes of the isotope coefficient between 0.25 and 0.5, in disagreement with Eliashberg theory which predicts a nearly constant isotope coefficient.We assign the pressure dependent isotope coefficient to Lifshitz...
The motion of the magnetic flux quanta in the mixed state of a type-II superconductor, due to the Lorentz force of an electric transport current, represents the key mechanism for generating resistive losses. Whereas the most common result is Joule heating of the superconductor, also purely electronic non-equilibrium effects can play a dominant role in the case of effective cooling of the sample. The...
R(O,F)BiS2 (R: La, Ce, Pr, Nd) superconducting single crystals with different F concentrations are grown using a CsCl/KCl flux. The obtained 1-2 mm-sized single crystals have a plate-like shape and are cleavable along the ab-plane. The crystal structure is tetragonal of space group P4/nmm (#129). The as-grown single crystals exhibit superconductivity at around 3–5 K. The superconducting transition...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.