CORRELATIONAL ANALYSIS OF SUPERCONDUCTING MIXED COPPER OXIDES (original) (raw)
The Unconventional Copper Oxide Superconductor with Conventional Constitution
Journal of Superconductivity and Novel Magnetism, 2019
A new Ba2CuO4-y superconductor with critical temperature (Tc) exceeding 70 K was discovered. The X-ray absorption measurement gives evidence that this cuprate resembles La2CuO4 but is doped with a fairly large amount of holes, while in contrast to the so far known hole-doped high-Tc cuprates, the new cuprate possesses a much shorter local apical oxygen distance as well as much expanded in-plane Cu–O bond, leading to unprecedented compressed local octahedron. In compressed local octahedron, the Cu3d3z2–r2 orbital level will be lifted above the Cu3dx2-y2 orbital level with more three-dimensional features, implying that pairing symmetry may carry admixtures from more than one gap, suggesting that Ba2CuO4-y composed of alkaline earth copper oxides that are the essential elements to form cuprate superconductors may belong to a new branch of cuprate superconductors.
CRYSTAL STRUCTURES OF CUPRATE BASED SUPERCONDUCTING MATERIALS
The high-T c cuprate superconductors have their structure derived from ideal perovskite structure, either through an intergrowth phenomenon or by an ordered removal of oxygen atoms. The common features of the cuprate superconductors are their layered crystal structure consisting of one or more CuO 2 layers. The tetragonal cuprate superconductors shows small difference in lattice parameters a and b close to 0.38nm because of common structural features of the CuO 2 planes. In this paper, the crystal structures of cuprate based superconductors are discussed
Pairing interactions and pairing mechanism in high-temperature copper oxide superconductors
Physical Review B, 2005
The polaron binding energy Ep in undoped parent cuprates has been determined to be about 1.0 eV from the unconventional oxygen-isotope effect on the antiferromagnetic ordering temperature. The deduced value of Ep is in quantitative agreement with that estimated from independent optical data and that estimated theoretically from the measured dielectric constants. The substantial oxygenisotope effect on the in-plane supercarrier mass observed in optimally doped cuprates suggests that polarons are bound into the Cooper pairs. We also identify the phonon modes that are strongly coupled to conduction electrons from the angle-resolved photoemission spectroscopy, tunneling spectra, and optical data. We consistently show that there is a very strong electron-phonon coupling feature at a phonon energy of about 20 meV along the antinodal direction and that this coupling becomes weaker towards the diagonal direction. We further show that high-temperature superconductivity in cuprates is caused by strong electron-phonon coupling, polaronic effect, and significant coupling with 2 eV Cu-O charge transfer fluctuation.
Materials Science and Engineering: R: Reports, 1999
A systematic view stemmed for the most important parts from the authors' own research results is presented for tailoring high-T c superconductive copper oxides from the standpoint of materials chemistry. The present article first elucidates that, in the multi-layered superconductive copper-oxide structures presently known to exist, the distribution of charge/charge carriers is inhomogeneous over several different spatial dimensions throughout the crystal. At the same time useful guiding rules are derived based on the concepts of tolerance parameter and bondvalence for controlling the charge distribution. Then experimental and semi-experimental evidences are presented to establish the relationships between the inhomogeneous distribution of holes and superconducting properties. To reach this goal, phenomenological aspects of the high-T c superconductive copper oxides are described systematically, and selected important techniques for estimating the local carrier concentration and distribution are discussed. That is, the following points are included in the present article: (i) general crystallographic categorization and naming scheme of multi-layered copper oxides based on the concept of homologous series, (ii) crystallographic and chemical factors to control the oxygen non-stoichiometry and charge distribution, (iii) techniques for probing the charge/carrier distribution in the layered copper-oxide crystal, and (iv) empirical relationships between the carrier distribution and superconducting properties including the superconductivity transition temperature, T c , the magnetic irreversibility field, H irr , and the so-called peak effect/fishtail phenomenon. Finally, the unified view is summarized and some indespensable questions to be still answered in future work are mentioned.
Mixed Layers in Copper Based Superconducting Materials
Microscopy Microanalysis Microstructures, 1996
2014 Recently discovered series of high Tc superconductors, characterized by the existence of two types of cations within the same layer, are presented. The first family concerns the mercury based cuprates, Hg1-xMxA2Cam-1CumO2m+2+03B4, with A = Ba and/or Sr, which exhibit structures closely related to that of the thallium cuprates TlBa2Cam-1CumO2m+3. They differ from the thallium cuprates by a high oxygen deficiency at the level of the mercury layer. It is shown that cations such as M
Competition between the pseudogap and superconductivity in the high-Tc copper oxides
Nature, 2009
A pairing gap and coherence are the two hallmarks of superconductivity. In a classical BCS superconductor they are established simultaneously at T c . In the cuprates, however, an energy gap (pseudogap) extends above T c [1, 2, 3,. The origin of this gap is one of the central issues in high temperature superconductivity. Recent experimental evidence demonstrates that the pseudogap and the superconducting gap are associated with different energy scales . It is however not clear whether they coexist independently or compete . In order to understand the physics of cuprates and improve their superconducting properties it is vital to determine whether the pseudogap is friend or foe of high temperature supercondctivity . Here we report evidence from angle resolved photoemission spectroscopy (ARPES) that the pseudogap and high temperature superconductivity represent two competing orders. We find that there is a direct correlation between a loss in the low energy spectral weight due to the pseudogap and a decrease of the coherent fraction of paired electrons. Therefore, the pseudogap competes with the superconductivity by depleting the spectral weight available for pairing in the region of momentum space where the superconducting gap is largest. This leads to a very unusual state in the underdoped cuprates, where only part of the Fermi surface develops coherence.
Physical Review Letters, 1991
We show that the retarded interaction between quasiparticles on a 2D square lattice induced by the exchange of antiferromagnetic paramagnons leads uniquely to a transition to a superconducting state with d,. 2,2 symmetry. With a spin-excitation spectrum and a quasiparticle-paramagnon coupling determined by fits to normal-state experiments, we obtain high transition temperatures and energy-gap behaviors comparable to those measured for YBa2Cu307, YBa2Cu30663, and Lal~qSr() I~Cu04.
Oxygen hole content, charge-transfer gap, covalency, and cuprate superconductivity
2021
Significance Modern theoretical methods solve a long-standing mystery of cuprate high-temperature superconductivity, identifying crucial quantities that optimize the transition temperature. Superconducting cuprates have very different transition temperatures, and even if the optimal value of the superconducting transition temperature is obtained for a given parent compound by varying doping, there is no correlation between optimal doping and transition temperature. Instead, it has been found experimentally that the optimal transition temperature is controlled by oxygen hole content or by the size of the charge-transfer gap. Our calculations show that these two quantities are correlated and that together with covalency they lead to an effective superexchange interaction between copper atoms that ultimately controls the optimal superconducting order parameter. Experiments have shown that the families of cuprate superconductors that have the largest transition temperature at optimal do...
COMPARATIVE STUDY OF LAYERED STRUCTURE FORMULISMS FOR HIGH TEMPERATURE COPPER-OXIDE SUPERCONDUCTORS
iaeme
An effective two-dimensional dynamic interaction potential energy function has been developed to understand the pairing mechanism leading to high-TC superconductivity in copper-oxide superconductors. It has been carried out under perturbation approximation using Dyson diagrammatic formulism and the technique of Fourier transform by assuming layered structure of cooper-oxide superconductors as supported by X-ray diffraction and spectroscopic studies within the framework of BCS theory. Three different potentials namely Coulomb, Yukawa like and Modified have been employed. The effective two-dimensional dynamic interaction potential energy functions thus obtained are complex in nature ab-initio. The calculations of coupling strength, Coulomb repulsive parameter, transition temperature, relaxation time, resistivity, specific heat jump, energy gap and thermal conductivity are being carried out separately for each case taking LSCO as a sample. The calculated results calculations show that the coupling between Cu-O conducting layers makes the effective potential energy function more attractive and a less repulsive.
A Review on Cuprate Based Superconducting Materials
Advances in Nanoscience and Nanotechnology, 2019
When Bednorz and Müller discovered the superconductivity in a compound La-Ba-Cu-O in 1986, it was considered as a breakthrough in the research of the superconductivity. This leads to the discovery of the other cuprate superconductors, and immediately the transition temperature of the synthesized materials reached to the liquid nitrogen temperature. Today the maximum transition temperature of the cuprate superconductors changes from 35 K for La 2 −xSr x CuO 4 to 138 K for Hg 1−x Tl x Ba 2 Ca 2 Cu 3 Oy (the highest record under normal pressure, which extends to ∼160K at high pressure). High-temperature superconductivity in the Non-stoichiometric cuprate lanthanum barium copper oxide. The T c for this material was 35 K, well above the previous record of 23K. Thousands of publications examine the superconductivity in cuprates between 1986 and 2001, and Bednorz and Müller were awarded the Nobel Prize in Physics only a year after their discovery. From 1986 to 2008, many cuprate superconductors were identified, the most famous being yttrium barium copper oxide (YBa 2 Cu 3 O 7 , "YBCO" or "1-2-3"). Another example is bismuth strontium calcium copper oxide (BSCCO or Bi 2 Sr 2 Ca n Cu n+1 O 2n+6-d) with T c = 95-107 K depending on the n value. Thallium barium calcium copper oxide (TBCCO, Tl m Ba 2 Ca n−1 Cu n O 2n+m+2+δ) was the next class of high-T c cuprate superconductors with T c = 127 K observed in Tl 2 Ba 2 Ca 2 Cu 3 O 10 (TBCCO-2223) in 1988. The highest confirmed, ambient-pressure, T c is 135 K, achieved in 1993 with the layered cuprate HgBa 2 Ca 2 Cu 3 O 8+x. few months later, another team measured superconductivity above 150K in the same compound under applied pressure (153 K at 150 k bar).