High-temperature superconductivity

About: High-temperature superconductivity is a research topic. Over the lifetime, 7263 publications have been published within this topic receiving 175377 citations. The topic is also known as: high-temperature superconductivity.

Electronic and magnetic phase diagram in K(x)Fe(2-y)Se(2) superconductors.

Abstract: The correlation and competition between antiferromagnetism and superconductivity are one of the most fundamental issues in high temperature superconductors. Superconductivity in high temperature cuprate superconductors arises from suppressing an antiferromagnetic (AFM) Mott insulator1 while in iron-pnictide superconductors arises from AFM semimetals and can coexist with AFM orders2,3,4,5,6,7,8,9. This difference raises many intriguing debates on the relation between the two classes of high temperature superconductors. Recently, superconductivity at 32 K has been reported in iron-chalcogenide superconductors AxFe2−ySe2 (A = K, Rb and Cs)10,11,12. They have the same structure as that of iron-pnictide 122-system13,14,15. Here, we report electronic and magnetic phase diagram of KxFe2−ySe2 system as a function of Fe valence. We find a superconducting phase sandwiched between two AFM insulating phases. The two insulating phases are characterized by two distinct superstructures caused by Fe vacancy orders with modulation wave vectors of q1 = (1/5, 3/5, 0) and q2 = (1/4, 3/4, 0), respectively.

A new Y-based HTSC with Tc above 100 K

Abstract: In search of finding the dominant mechanism in high temperature superconductivity phenomena, the Y3Ba5Cu8O18 compound was synthesized through the standard solid-state reaction technique. Characteristic XRD experiment was performed on the samples and was analyzed by the MAUD software refinement program. The analysis results indicate a 358 phase structure with the initial nominal stoichiometry. The electrical resistivity and its behavior under different magnetic field were measured. The electrical resistivity indicates the transition temperature T c onset = 102 K with transition width ΔTc = 2.4 K. This is the first observation of such a high transition temperature in the Y-based compound. Application of magnetic field leads the resistivity curve to spread out below transition region, and Tc (ρ = 0) shifts to lower temperatures. Also, a small broadening is observed by the application of high magnetic field in the T c onset region.

Electronic structure of prototype AFe2As2 and ReOFeAs high-temperature superconductors: A comparison

Abstract: We have performed ab initio LDA calculations of the electronic structure of newly discovered prototype high-temperature superconductors AFe2As2 (A = Ba, Sr) and compared it with the previously calculated electronic spectra of ReOFeAs (Re = La, Ce, Pr, Nd, Sm). In all cases, we obtain almost identical densities of states in a rather wide energy interval (up to 1 eV) around the Fermi level. Energy dispersions are also very similar and almost two dimensional in this energy interval, leading to the same basic (minimal) model of the electronic spectra, determined mainly by Fe d orbitals of the FeAs layers. The other constituents, such as A ions or rare-earth Re (or oxygen states) are more or less irrelevant for superconductivity. LDA Fermi surfaces for AFe2As2 are also very similar to that of ReOFeAs. This makes the more simple AFe2As2 a generic system to study the high-temperature superconductivity in FeAs-layered compounds.

Observation of individual vortices trapped along columnar defects in high-temperature superconductors

Abstract: Many superconductors do not entirely expel magnetic flux—rather, magnetic flux can penetrate the superconducting state in the form of vortices Moving vortices create resistance, so they must be ‘pinned’ to permit dissipationless current flow This is a particularly important issue for the high-transition-temperature superconductors, in which the vortices move very easily1 Irradiation of superconducting samples by heavy ions produces columnar defects, which are considered2 to be the optimal pinning traps when the orientation of the column coincides with that of the vortex line Although columnar defect pinning has been investigated using macroscopic techniques3,4, it has hitherto been impossible to resolve individual vortices intersecting with individual defects Here we achieve the resolution required to image vortex lines and columnar defects in Bi2Sr2CaCu2O8+δ (Bi-2212) thin films, using a 1-MV field-emission electron microscope5 For our thin films, we find that the vortex lines at higher temperatures are trapped and oriented along tilted columnar defects, irrespective of the orientation of the applied magnetic field At lower temperatures, however, vortex penetration always takes place perpendicular to the film plane, suggesting that intrinsic ‘background’ pinning in the material now dominates

Scaling behavior in electrical transport across grain boundaries in YBa 2 Cu 3 O 7 − δ superconductors

Abstract: We have found that the product of the critical current and the resistance of a grain-boundary junction scale with the resistance of the boundary. This scaling is observed to hold for a variety of samples prepared by evaporation or laser ablation and whose critical current density varies by three orders of magnitude.