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Title: Structural transitions, octahedral rotations, and electronic properties of A3Ni2O7 rare-earth nickelates under high pressure
Abstract

Motivated by the recent observation of superconductivity withTc ~ 80 K in pressurized La3Ni2O71, we explore the structural and electronic properties ofA3Ni2O7bilayer nickelates (A = La-Lu, Y, Sc) as a function of pressure (0–150 GPa) from first principles including a Coulomb repulsion term. At ~ 20 GPa, we observe an orthorhombic-to-tetragonal transition in La3Ni2O7at variance with x-ray diffraction data, which points to so-far unresolved complexities at the onset of superconductivity, e.g., charge doping by variations in the oxygen stoichiometry. We compile a structural phase diagram that establishes chemical and external pressure as distinct and counteracting control parameters. We find unexpected correlations betweenTcand thein-planeNi-O-Ni bond angles for La3Ni2O7. Moreover, two structural phases with significantc+octahedral rotations and in-plane bond disproportionations are uncovered forA = Nd-Lu, Y, Sc that exhibit a pressure-driven electronic reconstruction in the Niegmanifold. By disentangling the involvement of basal versus apical oxygen states at the Fermi surface, we identify Tb3Ni2O7as an interesting candidate for superconductivity at ambient pressure. These results suggest a profound tunability of the structural and electronic phases in this novel materials class and are key for a fundamental understanding of the superconductivity mechanism.

 
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NSF-PAR ID:
10502686
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
Nature Publishing Group
Date Published:
Journal Name:
npj Quantum Materials
Volume:
9
Issue:
1
ISSN:
2397-4648
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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