Magnetism in doped infinite-layer NdNiO2 studied by combined density functional theory and dynamical mean-field theory

TL;DR

This study combines advanced theoretical methods to understand the complex magnetic properties of doped NdNiO2, revealing how orbital splitting and self-doping effects influence magnetism and differ from cuprate superconductors.

Contribution

It provides a systematic theoretical analysis of magnetism in nickelates, highlighting the roles of orbital splitting and self-doping, which were not fully understood before.

Findings

Increased orbital splitting enhances magnetic moments but weakens magnetic exchange.

Self-doping by Nd-$d$$ orbitals screens Ni magnetic moments.

The magnetic behavior results from a competition between different magnetic states.

Abstract

The recent observation of superconductivity in infinite-layer nickelates has brought intense debate on the established knowledge of unconventional superconductivity based on the cuprates. Despite many similarities, the nickelates differ from the cuprates in many characteristics, the most notable one among which is the magnetism. Instead of a canonical antiferromagnetic Mott insulator as the undoped cuprates, from which the superconductivity is generally believed to arise upon doping, the undoped nickelates show no sign of magnetic ordering in experiments. Through a combined density functional theory, dynamical mean-field theory, and model study, we show that although the increased energy splitting between O-$p$ orbital and Cu/Ni-$d$ orbital ($\Delta_{dp}$) results in larger magnetic moment in nickelates, it also leads to stronger antiferromagnetism/ferromagnetism competition, and weaker magnetic exchange coupling. Meanwhile, the self-doping effect caused by Nd-$d$ orbital screens the magnetic moment of Ni. The Janus-faced effect of $\Delta_{dp}$ and self-doping effect together give a systematic understanding of magnetic behavior in nickelates and explain recent experimental observations.