Exploring the Natural Superlattices of High-pressure Superconductor La<sub>3</sub>Ni<sub>2</sub>O<sub>7</sub> and Nano-scale Effects of Topotactic Reduction in LaNiO<sub>2</sub> crystals
ORAL
Abstract
Rare-earth nickel oxides, known for their complex interplay between structure and properties, serve as a key platform for novel quantum phases and advanced applications. Topotactic transformations of perovskite nickelates have allowed precise control of oxygen vacancies, leading to the discovery of superconductivity in thin films of the infinite-layer (IL) nickelate Nd0.8Sr0.2NiO2 (1). In addition, the discovery of high-temperature superconductivity – with a superconducting transition of ~80 K – in La3Ni2O7 at elevated pressures (>14 GPa) has stimulated extensive research efforts (2). The fundamental properties of the superconducting phase have been the subject of controversial debates, including the interpretation of the possible filamentary character, whereas early investigations consistently postulated a crystal structure consisting of NiO6 octahedral bilayers stacked along the c-axis on La3Ni2O7.
Recently, we reported the unconventional structure of optical floating zone-grown high-pressure superconducting La3Ni2O7 single crystals (3) and the microstructural effects of topotactic reduction on the undoped LaNiO3 single crystals (4). Focusing on high-resolution scanning transmission electron microscopy (STEM) imaging and electron energy-loss spectroscopy (EELS) we reveal the multiple crystallographic phases in the La3Ni2O7 crystals, where the main phase is dominated by alternating monolayers and trilayers of NiO6 octahedra (3,5) different from the La3Ni2O7 systems composed of bilayer structures. Additionally, we demonstrate that the reduction process leads to different types of structural deformations in topotactically reduced LaNiO3 crystals (4).
References:
1. D. Li et al., Nature. 572, 624–627 (2019).
2. H. Sun et al., Nature. 621, 493–498 (2023).
3. P. Puphal et al., Phys. Rev. Lett. 133, 146002 (2024).
4. Y.-M. Wu et al., APL Materials. 12, 091119 (2024).
5. X. Chen et al., J. Am. Chem. Soc. 146, 3640–3645 (2024).
Recently, we reported the unconventional structure of optical floating zone-grown high-pressure superconducting La3Ni2O7 single crystals (3) and the microstructural effects of topotactic reduction on the undoped LaNiO3 single crystals (4). Focusing on high-resolution scanning transmission electron microscopy (STEM) imaging and electron energy-loss spectroscopy (EELS) we reveal the multiple crystallographic phases in the La3Ni2O7 crystals, where the main phase is dominated by alternating monolayers and trilayers of NiO6 octahedra (3,5) different from the La3Ni2O7 systems composed of bilayer structures. Additionally, we demonstrate that the reduction process leads to different types of structural deformations in topotactically reduced LaNiO3 crystals (4).
References:
1. D. Li et al., Nature. 572, 624–627 (2019).
2. H. Sun et al., Nature. 621, 493–498 (2023).
3. P. Puphal et al., Phys. Rev. Lett. 133, 146002 (2024).
4. Y.-M. Wu et al., APL Materials. 12, 091119 (2024).
5. X. Chen et al., J. Am. Chem. Soc. 146, 3640–3645 (2024).
–
Presenters
-
Y. Eren Suyolcu
- Max Planck Institute for Solid State Research