Lattice instability and high-Tcsuperconductivity inLa2−

Abstract

Lai.85Bao.i5Cu04 exhibits high-7" c superconductivity with an onset temperature near 33 K as measured by resistivity and magnetic susceptibility. The nonsuperconducting end-member compound, La2CuC>4, which has an orthorhombic, Cmca, structure, exhibits semiconducting behavior. The orthorhombic distortion is proposed to result from a Peierls 2&F instability or a soft zone-boundary phonon mode. The role of Ba is to suppress the instability and stabilize a higher-symmetry tetragonal, I4/mmm, structure which is metallic and superconducting.

Structure of (CuO)2 double layers in superconducting YBa2Cu3O7

“…Another type of planar defect was found [13] to exist at the mirror plane locations (z=O or z=l/2) in ErBa2Cu307. The defect, an inclusion of an extra layer leading to a c axis dimension of about 1.36 nm, was shown to be a double Er layer with a stacking order similar to the double LaO layer in La2SrxCu04 [2]. Furthermore [100] 900 rotation twins, across which the b axis aligns with a c axis, have also been studied [15].…”

“…[10] report the existence o(two extra layers (one Y layer and one CuO layer) inserted at the position of the CuO layer (z=O). Viegers et al [12] report defects at the grain boundary having a lattice parameter of 1.38 nm instead of the 1.16 nm characteristic of the 2 …”

“…The superconducting compound in the original mixture was rapidly identified as La1.85Ba0.15Cu04 [2], and subsequent research concentrated on the most suitable cation substitutions in this compound. A new oxide with a considerably higher T c was very soon found in the phase system Y 203-BaO-CuO [3], later identified by several groups as YBa2Cu307-8 [4], and now commonly known as the 1-2-3 compound.…”

Preparation of nanoparticles of silver halides, superconductors and magnetic materials using water-in-oil microemulsions as nano-reactors

“…The conventional method for the preparation of oxide superconductors by solid state reaction has many inherent problems like poor homogeneity, large particle size, lack of reproducibility, and longer heat treatment times. In order to achieve a better level of homogeneity, wet chemical techniques such as coprecipitation [129][130][131][132], freeze drying [133], amorphous citrate process [134,135], and chelation [136] have been used. One can achieve an even better level of homogeneity and smaller particle sizes if the wet chemical reactions are carried out in constrained nanosize reactors, like the aqueous droplets of water-in-oil microemulsions.…”

Reconciliation of local and long-range tilt correlations in underdopedLa2−xBaxCuO4(0≤xBožin1, Zhong2, Knox3 et al. 2015Phys. Rev. B297190View full textAdd to dashboardCite

“…Since the discovery of high-temperature superconductivity in La 2−x Ba x CuO 4 [1], the connection between the lattice and electronic structures has been the subject of considerable attention [2,3]. The further discovery [4] of the "1/8 anomaly"-a dramatic dip in the superconducting transition temperature T c at the dopant concentration of x = 1/8-motivated careful powder diffraction studies of the structural phase diagram [5][6][7][8].…”