Atomic Visualization of Copper Oxide Structure in Infinite-Layer Cuprate SrCuO2

TL;DR

This study provides atomic-scale visualization of the structure of SrCuO2 thin films, revealing surface reconstructions and symmetry breaking that are crucial for understanding high-temperature superconductivity in cuprates.

Contribution

It offers detailed atomic-level structural insights into SrCuO2 thin films, including surface reconstructions and symmetry breaking, advancing understanding of cuprate superconductors.

Findings

Identification of 2x2 surface reconstruction in CuO2 planes

Observation of intra-unit-cell rotational symmetry breaking

Detection of incommensurate stripe structures after annealing

Abstract

We report on atomic-scale visualization of the structure of infinite-layer cuprate SrCuO2 thin films grown on Nb-doped SrTiO3 substrates by molecular beam epitaxy. In-situ scanning tunneling microscopy study reveals stoichiometric copper oxide (CuO2) plane with a 2 x 2 surface reconstruction, prompted by preferential clustering of four adjacent CuO2 plaquettes. By imaging the subsurface Sr atoms, intra-unit-cell rotational symmetry breaking is observed, which, together with the adjacent CuO2 clustering, can be well accounted for by a periodic up-down buckling of oxygen ions on the CuO2 plane. Further post-annealing leads to an incommensurate stripe structure of the surface layer. Our findings provide important structural information for deeply understanding the electronic structure of superconducting CuO2 plane as well as high temperature superconductivity in cuprates.