Ordering and multiple phase transitions in ultra-thin nickelate superlattices

TL;DR

This paper uses advanced ab initio calculations to analyze multiple phase transitions in ultra-thin LaNiO₃/LaAlO₃ superlattices, revealing complex structural, magnetic, and electronic changes.

Contribution

It provides a detailed theoretical interpretation of observed phase transitions, identifying their nature and temperature points, and explains the underlying mechanisms.

Findings

Ground state is insulating, charge-ordered, and antiferromagnetic.

Transitions at 40 K and 150 K involve magnetic disorder and structural changes.

The high-temperature phase is a metallic Pauli paramagnet with a cuprate-like Fermi surface.

Abstract

We interpret via advanced ab initio calculations the multiple phase transitions observed recently in ultra-thin LaNiO$_{3}$/LaAlO$_{3}$ superlattices. The ground state is insulating, charge-ordered, and antiferromagnetic due to concurrent structural distortion and weak valency disproportionation. We infer distinct transitions at 40 K and 150 K, respectively, from antiferromagnetic order to moment disorder, and from structurally-dimerized insulator to an undistorted metallic Pauli paramagnet (exhibiting a cuprate-like Fermi surface). The results are in satisfactory agreement with experiment.