Long-Range Structural Order in a Hidden Phase of Ruddlesden–Popper Bilayer Nickelate La<sub>3</sub>Ni<sub>2</sub>O<sub>7</sub>
Haozhe Wang, Long Chen, Aya Rutherford, Haidong Zhou, Weiwei Xie
Abstract
High Resolution Image Download MS PowerPoint Slide The recent discovery of superconductivity in the Ruddlesden–Popper bilayer nickelate, specifically La 3 Ni 2 O 7, has generated significant interest in the exploration of high-temperature superconductivity within this material family. In this study, we present the crystallographic and electrical resistivity properties of two distinct Ruddlesden–Popper nickelates: the bilayer La 3 Ni 2 O 7 (referred to as 2222-phase) and a previously uncharacterized phase, La 3 Ni 2 O 7 (1313-phase). The 2222-phase is characterized by a pseudo F -centered orthorhombic lattice, featuring bilayer perovskite [LaNiO 3 ] layers interspaced by rock salt [LaO] layers, forming a repeated ...2222... sequence. Intriguingly, the 1313-phase, which displays semiconducting properties, crystallizes in the Cmmm space group and exhibits a pronounced predilection for a C -centered orthorhombic lattice. Within this structure, the perovskite [LaNiO 3 ] layers exhibit a distinctive long-range ordered arrangement, alternating between single- and trilayer configurations, resulting in a ...1313... sequence. This report contributes to novel insights into the crystallography and the structure–property relationship of Ruddlesden–Popper nickelates, paving the way for further investigations into their unique physical properties.