A 4-unit-cell superstructure in optimally doped YBa2Cu3O6.92 superconductor

TL;DR

This study reveals a 4-unit-cell superstructure coexisting with superconductivity in optimally doped YBCO, characterized by complex atomic displacements and Ortho-IV nanodomains, using high-energy diffraction techniques.

Contribution

It uncovers a specific superstructure and nanodomain formation in YBCO, providing new insights into its atomic-scale organization related to superconductivity.

Findings

Detection of a 4-unit-cell superstructure with q0=(1/4,0,0)

Presence of anisotropic atomic displacements in multiple planes

Correlation of displacements over 3-6 unit cells indicating nanodomains

Abstract

Using high-energy diffraction we show that a 4-unit-cell superstructure, q0=(1/4,0,0), along the shorter Cu-Cu bonds coexists with superconductivity in optimally doped YBCO. A complex set of anisotropic atomic displacements on neighboring CuO chain planes, BaO planes, and CuO2 planes, respectively, correlated over ~3-6 unit cells gives rise to diffuse superlattice peaks. Our observations are consistent with the presence of Ortho-IV nanodomains containing these displacements.