The crystal structure of superconducting La2CuO4.032 by neutron diffraction

Abstract

The structure of superconducting La,CuO,,o,, has been determined by singlecrystal neutron diffraction data. The excess oxygen, 0 4 , is located between two adjacent La01 layers. The presence of 04 distorts the apical-oxygen 01 sublattice in such that each 0 4 forms a short bond (1.64A) with one 01, which indicates the formation of a strong covalent bond between these two atoms. The Cu and 0 2 sublattices as well as that of La are not affected by 0 4 , however, 1.6% of the La cations increase their coordination from 9 to 10.

Electronically driven superconductor-insulator transition in electrostatically doped La2CuO4+δthin films

“…They exhibit staging order in the direction perpendicular to the CuO 2 planes, and they form inplane stripes along the main diagonal of the tetragonal unit cell breaking the symmetry of the Cu-O octahedra along the main in-plane directions of the pseudocubic unit cell. 16 The expected pattern of disorder in this family of compounds is therefore weaker than that obtained for chemically substituted compounds. 17 δ-LCO crystals are believed to be the simplest cuprate HTS since the i-O are not randomly distributed, and moreover, they have the highest T C since the i-O are located far away from the superconducting CuO 2 planes.…”

A survey of the Van Hove scenario for high-tc superconductivity with special emphasis on pseudogaps and striped phases

“…The phase separation begins at about 300K, and is arrested around 200K, when the oxygen diffusion becomes too slow to stay in equilibrium [655,681,680,581]. Figure 61 is a composite phase diagram based on the work of several groups [682,156].…”

Thermally activated dynamics of the tilts of the CuO6octahedra, hopping of interstitial O, and possible instability towards the LTT phase in La2CuOCordero1, Grandini2, Cannelli3 et al. 1998Phys. Rev. B365240View full textAdd to dashboardCite

“…If these double potentials are partly due to the fact that tϽ1, then a relief of the stresses between LaO and CuO 2 planes should result in a decrease of both the distance between the potential minima and of the barrier, i.e., in a decrease of the activation energy; a reduction of the average tilt angle of the octahedra with doping is actually observed. 40,6 The reduction of the activation energy implies a faster rate for the hopping between the possible configurations and therefore the maximum of the anelastic relaxation intensity, which occurs around ϭ1, is shifted to lower temperature. The same argument holds for peak L, even if the relaxation dynamics is not describable by the classical rate theory; also when tunneling dominates, a reduction of the barrier results in faster rates and therefore in a shift to lower temperature of the corresponding relaxation process.…”