Two-Dimensional Nanogranularity of the Oxygen Chains in the YBa2Cu3O6.33 Superconductor

Abstract

The organization of dopants in high temperature superconductors provides complex topological geometries that controls superconducting properties. This makes the study of dopants spatial distribution of fundamental importance. The mobile oxygen ions, y, in the CuO 2 plane of YBa 2 Cu 3 O 6+y (0.33<y<0.67) form ordered chains which greatly affect the transport properties of the material. Here we visualize and characterize the 2D spatial organization of these oxygen chains using scanning micro X-ray diffraction measurements in transmission mode on a thin single crystal slab with y=0.33 (T c =7 K) near the critical doping for the insulator-to-metal transition. We show the typical landscape of percolation made of a granular spatial pattern due the oxygen chains segregating in quasi-onedimensional needles of Ortho II (O-II) phase embedded in an insulating matrix with low density of disordered oxygen interstitials. High temperature superconductors, constitute an intriguing class of materials where the separation and competition of multiple phases at nanoscopic scale occurs [7][8][9][10][11]. These inhomogeneous phases are due to the ordering of dopants and competition between short range charge, spin and orbital density wave order (CDW, SDW, ODW) inhomogeneity. As a result, new complex geometries emerge, where quantum coherence develops [12][13][14]. Thus, the study of local features by using high resolution experimental probes assumes a paramount importance for the a deeper understanding of new complex and heterogeneous materials. Local probes such as X ray Absorption experimental methods (XANES and EXAFS) and high resolution X ray and neutron diffraction have been used for investigating structural inhomogeneity in various systems such as diborides [15][16][17] and cuprates [18][19][20]. In the last years, the possibility to focus X ray beam onto micrometric and sub-micrometric areas, has allowed to probe the local structure with high resolution in

On the dilemma between percolation processes and fluctuating pairs as the origin of the enhanced conductivity above the superconducting transition in cuprates

“…Since the earlier results commented above, a number of studies have addressed the influence of possible chemical, structural and electronic disorder on the behavior of different observables around T c in cuprate superconductors [38][39][40][41][42][43]. However, the dilemma between fluctuating superconducting pairs and percolation processes remains at present an open and debated question, despite the relevance of understanding the emergence of the superconductivity in these materials at a phenomenological level [11,32,[44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63]. To contribute to answering that question, detailed ρ ab (T) data, previously measured in high quality crystals and films of La 1.85 Sr 0.15 CuO 4 (LaSCO/0.15), Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212), and Tl 2 Ba 2 Ca 2 Cu 3 O 10 (Tl-2223), will be analyzed here [43,[64][65][66].…”

Lattice, Charge, and Spin Phase Inhomogeneity in Complex-Striped Quantum Matter

“…In the field of cuprates evidence for percolation of nanoscale puddles of the dopant oxygen chains in YBa 2 Cu 3 O 6.33 has been observed at the insulator to metal transition [24].…”