Doping-dependent character and possible magnetic ordering of NdNiO$_2$

TL;DR

This paper investigates the complex electronic and magnetic properties of NdNiO$_2$, revealing doping-dependent behaviors, the coexistence of different correlated phases, and potential magnetic ordering relevant for understanding nickelate superconductors.

Contribution

It provides a detailed theoretical analysis of the doping-dependent electronic structure and magnetic tendencies in NdNiO$_2$ using advanced dynamical mean-field theory.

Findings

Doped NdNiO$_2$ exhibits a transition from a Mott insulator to a Hund metal.

Fermi-level crossing of Ni-$d_{z^2}$ flat band links different regimes for superconductivity.

Antiferromagnetic order with small Ni moments is a significant competing phase at low temperatures.

Abstract

The novel nickelate superconductors of infinite-layer type feature challenging electronic pecularities in the normal-state phase diagram with doping. Distinct many-body behavior and different dispersion regimes of the entangled $\{$Ni-$d_{z^2}$, Ni-$d_{x^2-y^2}$$\}$ orbital sector give rise to highly rich physics, which is here studied for the case of the NdNiO$_2$ system. An analysis based on advanced realistic dynamical mean-field theory unveils that the superconducting hole-doped region is the meeting place of a (self-)doped Mott insulator from the underdoped side, and a bad Hund metal from the overdoped side. Fermi-level crossing of the Ni-$d_{z^2}$ flat-band ties both regimes together to form a singular arena for unconventional superconductivity. We furthermore shed light on the intriguing problem of elusive magnetism in infinite-layer nickelates. Antiferromagnetic (AFM) order with small Ni moments is shown to be a vital competitor at low temperature. At stoichiometry, C-AFM order with ferromagnetic spin-alignment along the $c$-axis benefits from a conceivable coexistence with Kondo(-lattice) screening.