Charge and magnetic orders in a two-band model with long-range interactions for infinite-layer nickelates NdNiO$_2$

TL;DR

This study develops an effective two-band model for NdNiO$_2$ to explore magnetic and charge orders, revealing weak charge modulation and magnetic order suppression due to quantum fluctuations, with bands largely uncoupled.

Contribution

It introduces a two-band model incorporating intersite Coulomb interactions and analyzes magnetic and charge orders using variational cluster and mean-field methods, highlighting the effects of quantum fluctuations.

Findings

Weak charge modulation possibly due to finite-size effects

Magnetic order depends on $d$-band filling and is suppressed by quantum fluctuations

Bands remain largely uncoupled despite inter-orbital Coulomb interactions

Abstract

We present an effective two-band model for infinite-layer nickelates NdNiO$_2$ that consisting of a $d$ band centered at Ni site and an interstitial $s$-like band centered at Nd site. To the large extent of the wave functions, we find intersite Coulomb interactions to be substantial. We then use the variational cluster approach together with mean-field theory to investigate magnetic and charge ordering. While tendencies towards charge modulation are found, they are weak and might be due to finite-size effects. Magnetic order is determined mostly by the filling of the $d$ band and hardly affected by including longer-ranged interactions. For a $d$-band density consistent with density-functional theory, magnetic ordering vanishes once quantum fluctuations are included to a sufficient spatial extent. Apart from self-doping, $d$ and $s$ bands remain largely uncoupled despite the presence of inter-orbital Coulomb interaction and (small) inter-orbital hopping.