Role of $4f$ states in infinite-layer NdNiO${}_2$

Abstract

Atomic $4f$ states have been found to be essential players in the physical behavior of lanthanide compounds, at the Fermi level $E_F$ as in the proposed topological Kondo insulator SmB${}_6$, or further away as in the magnetic superconductor system $\mathcal{R}$Ni${}_2$B${}_2$C ($\mathcal{R}$=rare earth ion) and in Y${}_{1-x}$Pr${}_x$Ba${}_2$Cu${}_3$O${}_7$, where the $4f$ shell of Pr has a devastating effect on superconductivity. In hole-doped $\mathcal{R}$NiO${}_2$, the $\mathcal{R}$=Nd member is found to be superconducting while $\mathcal{R}$=La is not, in spite of the calculated electronic structures being nearly identical. We report first principles results that indicate that the Nd $4f$ moment affects states at $E_F$ in infinite-layer NdNiO${}_2$, an effect that will not occur for LaNiO${}_2$. Treating 20% hole-doping in the virtual crystal approach indicates that 0.15 holes empty the $\Gamma$-centered Nd-derived electron pocket while leaving the other electron pocket unchanged; hence Ni only absorbs 0.05 holes; the La counterpart would behave similarly. However, coupling of $4f$ states to the electron pockets at $E_F$ arises through the Nd intra-atomic $4f-5d$ exchange coupling $K\approx 0.5$ eV and is ferromagnetic (FM), i.e. anti-Kondo, in sign. This interaction causes spin-disorder broadening of the electron pockets and should be included in models of the normal and superconducting states of Nd${}_{0.8}$Sr${}_{0.2}$NiO${}_2$ The Ni moments differ by 0.2${\mu }_B$ for FM and antiferromagnetic alignment (the latter are larger), reflecting some itineracy and indicating that Heisenberg coupling of the moments may not provide a quantitative modeling of Ni-Ni exchange coupling.

13 pages with Supplemental Material

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• Fluctuation-frustrated flat band instabilities in NdNiO2
• Phase diagram of nickelate superconductors calculated by dynamical vertex approximation
• Dynamical Mean Field Studies of Infinite Layer Nickelates: Physics Results and Methodological Implications
• Infinite-layer nickelate superconductors: A current experimental perspective of the crystal and electronic structures
• Electronic structure and magnetic properties of higher-order layered nickelates: La${}_{n+1}$Ni${}_n$O${}_{2n+2}$ ($n=4-6$)
• Correlated interface electron gas in infinite-layer nickelate versus cuprate films on SrTiO${}_3$(001)
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• Spin-density, charge- and bond-disproportionation wave instability in hole-doped infinite-layer $R$NiO${}_2$
• Proposed ordering of textured spin singlets in a bulk infinite layer nickelate
• Magnetism in doped infinite-layer NdNiO2 studied by combined density functional theory and dynamical mean-field theory
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• Observation of Coulomb blockade and Coulomb staircases in superconducting Pr0.8Sr0.2NiO2 films
• Conductivity of infinite-layer NdNiO${}_2$ as a probe of spectator bands
• Influence of $f$ Electrons on the Electronic Band Structure of Rare-Earth Nickelates
• A $d^8$ anti-Hund's Singlet Insulator in an Infinite-layer Nickelate