Overlooked transportation anisotropies in d-band correlated rare-earth perovskite nickelates

TL;DR

This paper reveals unexpected anisotropies in electronic transport in rare-earth nickelate perovskites caused by orbital effects and strain, despite their symmetric structures, opening new avenues for enhancing their transport properties.

Contribution

It uncovers the intrinsic and extrinsic anisotropies in ReNiO3 perovskites driven by orbital and strain effects, challenging conventional expectations based on crystal symmetry.

Findings

Strain induces extrinsic anisotropies in orbital transitions and metal-insulator behavior.

In-plane orbital entropy causes intrinsic anisotropies affecting transport properties.

Anisotropic transport behaviors can be engineered by controlling orbital directionality and strain.

Abstract

Anisotropies in electronic transportations conventionally originate from the nature of low symmetries in crystal structures, and were not anticipated for perovskite oxides, the crystal asymmetricity of which is far below, e.g. van der Waals or topological crystal. Beyond conventional expectations, herein we demonstrate pronounced anisotropies in the inter-band coulomb repulsion dominated electronic transportation behaviors under low-dimensional confinement for the perovskite family of rare-earth nickelates (ReNiO3). From one aspect, imparting bi-axial interfacial strains upon various lattice planes results in extrinsic anisotropies in the abrupt orbital transitions of ReNiO3, and their metal to insulator transition behaviors that elevates the transition temperature beyond the existing merit. From the other aspect, the in-plane orbital entropy associated to the in-plane symmetry of the NiO6 octahedron within ReNiO3 causes intrinsic anisotropies for the gradually orbital transition with temperature to further improve their thermistor transportation properties. The present work unveils the overlooked role of the electronic orbital directionality within low dimensional correlated perovskites that can trigger anisotropic transportation behaviors, in spite of their relatively symmetric crystal structures. Establishing anisotropic transportations integrating the electron correlation and quantum confinement effects will bring in a new freedom for achieving further improvement in transportation properties of multi-functional perovskite oxides.