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 article, it was shown that the low-energy physics responsible for the high-T-c superconductivity of iron-based superconductors is essentially governed by an effective two-orbital Hamiltonian near half filling.
Abstract: Although iron-based superconductors are multiorbital systems with complicated band structures, we demonstrate that the low-energy physics which is responsible for their high-T-c superconductivity is essentially governed by an effective two-orbital Hamiltonian near half filling. This underlying electronic structure is protected by the S-4 symmetry. With repulsive or strong next-nearest-neighbor antiferromagnetic exchange interactions, the model results in a robust A(1g) s-wave pairing which can be mapped exactly to the d-wave pairing observed in cuprates. The classification of the superconducting (SC) states according to the S4 symmetry leads to a natural prediction of the existence of two different phases, named the A and B phases. In the B phase, the superconducting order has an overall sign change along the c axis between the top and bottom As (or Se) planes in a single Fe-As (or Fe-Se) trilayer structure, the common building block of iron-based superconductors. The sign change is analogous to the sign change in the d-wave superconducting state of cuprates upon 90 degrees rotation. Our derivation provides a unified understanding of iron pnictides and iron chalcogenides, and suggests that cuprates and iron-based superconductors share an identical high-T-c superconducting mechanism.
43 citations
TL;DR: The upper critical field Bc2 as discussed by the authors provides the most direct measure of the intrinsic anisotropy of a superconductor and has been shown to be at least 70% in the case of Tl2Ba2CaCuCu2Ox.
Abstract: The upper critical field Bc2 provides the most direct measure of the intrinsic anisotropy of a superconductor. For highly oriented, sputtered thin films of the high‐temperature superconductor Tl2Ba2CaCu2Ox, we find a Bc2 anisotropy of at least 70, which exceeds similar measurements on thin films and single crystals of the high‐temperature superconductors Bi‐Sr‐Ca‐Cu‐O and YBa2Cu3Oy. We discuss why the midpoints of the resistive transitions, used in these measurements, may be appropriate for defining the intrinsic Bc2.
43 citations
TL;DR: In this article, large, single-grains of (LRE)-Ba-Cu-O (light rare earth: Nd, Sm, and Gd) bulk high-temperature superconductors with significantly improved properties have been fabricated in an air atmosphere using a practical processing technique based on seeded infiltration growth.
Abstract: Large, single-grains of (LRE)-Ba–Cu–O (LRE=light rare earth: Nd, Sm, and Gd) bulk high-temperature superconductors with significantly improved properties have been fabricated in an air atmosphere using a practical processing technique based on seeded infiltration growth. This process involves the use of a generic seed crystal, developed recently at the IRC in Superconductivity, to promote epitaxial grain nucleation. The formation of a solid-solution phase within the nucleated single grain is then suppressed effectively by providing excess Ba to the growth front under an air processing atmosphere. Critical current densities in excess of 105A∕cm2 at 77K have been observed in the resulting large grain samples, with an associated and significant improvement in trapped magnetic field. This air-based seeded-infiltration-growth process offers a significant degree of freedom both in terms of the processing parameters and the reproducibility in growth of oriented single grains.
43 citations
TL;DR: In contrast to classic superconductors, the noise at the resistive transition does not arise from equilibrium temperature fluctuations as mentioned in this paper, and the ratio of the spectral density to the average voltage decreases markedly as the microstructure of the films is improved.
Abstract: Low-frequency voltage fluctuations in thin films of YBa/sub 2/Cu/sub 3/O/sub 7-x/ at and above the superconducting transition temperature have a spectral density proportional to the ratio of the average voltage across the film to the frequency. The ratio of the spectral density to the average voltage decreases markedly as the microstructure of the films is improved. In contrast to classic superconductors, the noise at the resistive transition does not arise from equilibrium temperature fluctuations. >
42 citations
TL;DR: The microscopic model presented here reduces to the phenomenological Ginzburg-Landau, Lawrence-Doniach, and anisotropic London models in the appropriate limits, and is used to examine the role of dimensionality and interlayer scattering on the magnetic properties of layered superconductors.
Abstract: We develop a microscopic model of layered superconductors, designed specifically for the high-${\mathit{T}}_{\mathit{c}}$ cuprates, which is valid at all temperatures below the degeneracy temperature and for all relevant length scales. The model is based on the original idea of Bulaevskii, and consists of a stack of two-dimensional conducting planes coupled via interlayer diffusion of charge carriers. The microscopic model presented here reduces to the phenomenological Ginzburg-Landau, Lawrence-Doniach, and anisotropic London models in the appropriate limits. We derive the main equations of the interlayer diffusion model, then use the model to examine the role of dimensionality and interlayer scattering on the magnetic properties of layered superconductors.
42 citations