High-Tc Superconductivity in Cu Oxides (original) (raw)
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Crystal chemistry and superconductivity of the copper oxides
Journal of Solid State Chemistry, 1990
simplest system Lar.+k,CuO~ (Ln = lanthanide) depending upon the size of Ln and the value ofy. The internal electric field created by the formal charges in the adjacent layers modulates the distribution of holes between the active and inactive layers and the influence of Pr on superconductivity. The coordination geometry preferred by different oxidation states of Cu appears to control the oxygen ordering and the T, variation in the YBa&Or,+, y s stem. The c-axis Cu-0 distance modulates the width of the conduction band and the electronic properties. Chemical characterization of the thallium cuprates has demonstrated that the oxidation of the Tlr-,BarCa,-IC~n02n+4-x s stem can be due to either solely an overlap y of the Tl : 6s band with the conduction band or solely Tl vacancies, depending upon the value of y; as normally prepared, both effects are operative.
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).
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.
Superconductivity in the ‘triple-fluorite-layer’ copper oxides (Cu,M)-1232 (M=Mo, W, Re, Pb)
Solid State Communications, 2006
Here two new high-T c superconductors are reported of the (Cu,M)-1232 structure containing a fluorite-structured (Ce,Y)-O 2-(Ce,Y)-O 2-(Ce,Y) triple-layer block between two adjacent superconductive CuO 2 planes. The new superconductors were found through substitution studies at the Mo site in the recently synthesized superconductor, (Cu 0.75 Mo 0.25)Sr 2 (Ce 0.67 Y 0.33) 3 Cu 2 O 11Cd or (Cu 0.75 Mo 0.25)-1232 [Y. Morita, T. Nagai, Y. Matsui, H. Yamauchi, M. Karppinen, Phys. Rev. B 70 (2004) 174515. [10a]]. Essentially single-phase samples of the (Cu 0.75 M 0.25)-1232 phase with MZW, Re and Pb were obtained by an ambient-pressure solid-state synthesis method. Through a subsequent high-pressure oxygenation (HPO) treatment carried out at 5 GPa and 500 8C in the presence of Ag 2 O 2 as an oxygen source the MZW and Re samples were successfully 'superconductorized'. Introduction of Pb was found to markedly enhance the speed of the formation of the 1232 phase, but the (Cu,Pb)-1232 samples did not exhibit superconductivity. Among the superconductive (Cu,M)-1232 samples, the highest T c value of 56 K was achieved for (Cu 0.75 Re 0.25)-1232. It is likely that the higher the average valence of cations in the (Cu,M)O 1Cd charge-reservoir is, the more can the phase accommodate excess oxygen upon HPO treatment and the higher is the resulting T c value.
CORRELATIONAL ANALYSIS OF SUPERCONDUCTING MIXED COPPER OXIDES
A unifying structural scheme of all layered superconducting cuprates is proposed. The paper is a review based on a three level correlational analysis of the behaviour of one compound, of a homologous series and a third interseries analysis, revealing multiple correlation between the critical temperature value and different bond lengths via the oxygen content.
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.
Pramana, 1988
Several oxides of the Bi,.M,CupOx family (m=2,3; n=2,3,4; p= 1,2,3 and M = alkaline earth or Bi), possessing structures similar to the Aurivitlius family of oxides, show high I", superconductivity.
Review of High Temperature Superconductors and Application in Various Fields 763
Research & Development in Material Science, 2018
The layered perovskite cuprate materials are a unique class of superconductors with unusual normal-state and superconducting properties. The common physics to all these materials is that of the underlying CuO 2 planes. This review provides a survey of and guide to their physical properties as it relates to the superconductivity of this interesting group of conducting oxides. The present statuses on applications of cuprate based high-temperature superconductors have been included. In this paper, all characteristics of cuprate based superconductors depending upon the recent discoveries and applications of those compounds have been included and explained so that a researcher can get a good idea about this field easily. The article gives a summary of the prevailing arguments of researchers to relate the material to cuprates and the comparative features of many families of 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
High-Tc superconductivity in three-fluorite-layer copper oxides. I. (Hg,W)Sr2(Ce,Eu)3Cu2O11+δ
Physical Review B, 2004
We have synthesized high-quality samples of the s = 3 member of the ͑Cu, Mo͒-12s2 homologous series of layered copper oxides. The ͑Cu, Mo͒-1232 phase forms as a single phase for the cation composition ͑Cu 0.75 Mo 0.25 ͒Sr 2 ͑Ce 0.67 Y 0.33 ͒ 3 Cu 2 O 11+␦ through solid-state synthesis in air, but the samples as synthesized are not superconductive. Superconductivity is induced in the air-synthesized samples by means of high-pressure oxygenation carried out at 5 GPa and 500°C in the presence of Ag 2 O 2 as an excess oxygen source. With increasing ratio of Ag 2 O 2 to the ͑Cu, Mo͒-1232 phase the c-axis lattice parameter gradually decreases and T c increases. The highest T c value of 53 K reached for samples oxygenated in the presence of 100 mol% Ag 2 O 2 exceeds the values reported for Cu-based two-fluorite-layer compounds.