Topic
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.
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TL;DR: In this paper, the authors propose an explanation for the appearance of superconductivity at the interfaces of graphite with Bernal stacking order, where a network of line defects with flat bands appears at the interface between two slightly twisted graphite structures.
Abstract: We propose an explanation for the appearance of superconductivity at the interfaces of graphite with Bernal stacking order. A network of line defects with flat bands appears at the interfaces between two slightly twisted graphite structures. Due to the flat band the probability to find high temperature superconductivity at these quasi one-dimensional corridors is strongly enhanced. When the network of superconducting lines is dense it becomes effectively two-dimensional. The model provides an explanation for several reports on the observation of superconductivity up to room temperature in different oriented graphite samples, graphite powders as well as graphite-composite samples published in the past.
75 citations
TL;DR: In this article, it was shown that a single layer between the superconducting copper layers can possess effective pinning centers that are absent in the double layer cases, which is a prerequisite for obtaining a high critical current density (J c ) in a magnetic field.
Abstract: The presence of pinning centers in high temperature superconductors (HTSCs) is a prerequisite for obtaining a high critical current density ( J c ) in a magnetic field. We have discovered that, perhaps more generally, HTSCs having only a single layer between the superconducting copper layers (for example the YBaCuO or TlSrCaCuO systems) can possess effective pinning centers that are absent in the double layer cases. Several samples prepared by a partial melt process, with the nominal composition (Tl 0.5 Pb 0.5 ) 1 (Sr 0.8 Ba 0.2 ) 2 Ca 2 Cu 3 O 9 , showed the high intragrain J c , by the magnetization method, greater than 2 × 10 4 A/cm 2 at 77 K and 1 T. This result suggests that more effective pinning centers exist in the (1223) phase of the modified TlSrCaCuO system (ref. [1]). We propose an explanation why both YBa 2 Cu 3 O 7 and (1223) of TSCCO contain useful pinning centers, whereas both Bi- and Tl-double-layer superconductors do not. Effective pinning, in this case greater for single layers rather than double layers, is related to the strength of the superconductive order-parameter in these layers intervening the CuO layers.
75 citations
TL;DR: Experimental studies of the time decay of the nonequilibrium magnetization in high-temperature superconductors, a phenomenon known as magnetic relaxation, are reviewed.
Abstract: We review experimental studies of the time decay of the nonequilibrium magnetization in high-temperature superconductors, a phenomenon known as magnetic relaxation. This effect has its origin in motion of flux lines out of their pinning sites due to thermal activation or quantum tunneling. The combination of relatively weak flux pinning and high temperatures leads to rich properties that are unconventional in the context of low temperature superconductivity and that have been the subject to intense studies. The results are assessed from a purely experimental perspective and discussed in the context of present phenomenological theories. [S0034-6861(96)00403-5]
75 citations
01 Jan 1982
TL;DR: In this article, a review of the problems of high-temperature superconductivity is presented, and critical temperature considerations are given, and possible increases in critical temperature due to structural transition-induced electron spectrum changes are given.
Abstract: Possible methods of significantly raising the critical temperature of superconductors are presented, and the physical properties of applicable systems are examined. A review of the problems of high-temperature superconductivity is presented, and critical temperature considerations are given. In addition, attention is given to electron-phonon interaction in metals and lattice stability problems, superconductivity in three-dimensional quasi-isotropic systems, and possible increases in critical temperature due to structural-transition-induced electron spectrum changes. Finally, other topics discussed include electronic properties and superconductivity of layered crystals, properties of systems with one-dimensional anisotropy, sandwich type superconducting systems, and superconductivity under nonequilibrium conditions.
75 citations
TL;DR: In this paper, the ground state of the CuO 6 octahedron in La 2-x Sr x CuO 4 changes from 1 A 1 g to 3 B 1 g near the observed onset concentration of superconductivity.
Abstract: By the first-principles variational calculations we show that, with the increase of Sr concentration, the ground state of CuO 6 octahedron in La 2- x Sr x CuO 4 changes from 1 A 1 g to 3 B 1 g near the observed onset concentration of superconductivity while the ground state of the CuO 4 cluster in Nd 2- x Ce x CuO 4 is always 3 B 1 g in the presence of dopant electrons. Based on this result, two kinds of phase diagrams are predicted for hole- and electron-doped superconductors. These results support the spin polaron mechanism proposed by Kamimura et al .
75 citations