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.

Mercury-Based Cuprate High-Transition Temperature Grain-Boundary Junctions and SQUIDs Operating Above 110 Kelvin.

Abstract: The superconducting transport characteristics of HgBa2 CaCu2O6+δ (Hg-1212) films and grain-boundary junctions grown on (100)-oriented SrTiO3 bicrystal substrates have been investigated. The films exhibit a zero-resistance temperature of ∼120 kelvin and sustain large critical current densities, with values as high as 106 amperes per square centimeter at around 100 kelvin. On the other hand, the grain boundaries behave as weak links, with substantially lower critical currents, as is observed for other cuprate superconductors. A reduction of three orders of magnitude in critical current was observed for transport across a 36.8° grain boundary. The current-voltage characteristics of bridges across such a grain boundary show weak-link behavior qualitatively resembling that of a resistively shunted junction. Single-level direct-current superconducting quantum interference devices (SQUIDs) have been fabricated with such bicrystal junctions. These SQUIDs show clear periodic voltage modulations when subjected to applied magnetic fields. The SQUIDs operate at temperatures as high as 111.8 kelvin, which makes them attractive for operation in portable sensors and devices that utilize nonconventional cooling methods.

Universal behavior of the upper critical field in iron based superconductors

Abstract: The newly discovered iron-based high temperature superconductors have demonstrated rich physical properties. Here we give a brief review on the recent studies of the upper critical field and its anisotropy in a few typical series of the iron-based superconductors (FeSCs). In spite of their characters of a layered crystal structure, all the FeSCs possess an extremely large upper critical field and a weak anisotropy of superconductivity, being unique among the layered superconductors. These particular properties indicate potential applications of the FeSCs in the future. Based on the experimental facts of the FeSCs, we will discuss the possible mechanisms of pair breaking in high magnetic fields and its restrictions on the theoretical analysis of the superconducting pairing mechanisms.

Interface high-temperature superconductivity

Abstract: Cuprate high temperature superconductors consist of two quasi-two-dimensional (2D) substructures: CuO2 superconducting layers and charge reservoir layers. The superconductivity is realized by charge transfer from the charge reservoir layers into the superconducting layers without chemical dopants and defects being introduced into the latter, similar to modulation-doping in semiconductor superlattices of AlGaAs/GaAs. Inspired by this scheme, we have been searching for high temperature superconductivity in ultrathin films of superconductors epitaxially grown on semiconductor/oxide substrates since 2008. We have observed interface enhanced superconductivity in both conventional and unconventional superconducting films, including single atomic layer films of Pb and In on Si substrates and single unit cell (UC) films of FeSe on SrTiO3 (STO) substrates. The discovery of high temperature superconductivity with a superconducting gap of ~20 meV in 1UC-FeSe/STO has stimulated tremendous interest in superconductivity community, for it opens new avenue for both raising superconducting transition temperature and understanding the pairing mechanism of unconventional high temperature superconductivity. Here, we review mainly the experimental progress on interface enhanced superconductivity in the three systems mentioned above with emphasis on 1UC-FeSe/STO, studied by scanning tunneling microscopy/spectroscopy, angle-resolved photoemission spectroscopy and transport experiments. We discuss the roles of interfaces and possible pairing mechanism inferred from those studies.

Freezing of the vortex liquid in high-Tc superconductors: A density-functional approach.

Abstract: The structure of the unpinned vortex fluid in layered oxide high-temperature superconductors is investigated numerically using appropriate classical liquid-state theory, for magnetic fields {ital B} perpendicular to the layer plane. The direct correlation function so obtained is used as input for a first-principles, parameter-free calculation of the discontinuous fluid-to-Abrikosov-lattice transition boundary {ital T}{sub {ital f}}({ital B}). This transition boundary is found to have a shape and location similar to that observed in strongly anisotropic materials, e.g., Bi-Sr-Ca-Cu-O.

The calculated defect properties of La2CuO4 related to high-Tc superconductivity

Abstract: Calculations are reported of perfect lattice and defect properties of the orthorhombic and tetragonal phases of La2CuO4 related to high-T c superconductivity. The theoretical methods are broadly si...