未掺杂与空穴掺杂PrNiO$_2$中Pr混合价态的缺失
Absence of mixed valency for Pr in pristine and hole-doped PrNiO$_2$
AI总结：
本研究采用DFT+DMFT方法揭示PrNiO$_2$及其空穴掺杂变体中Pr 4f态为绝缘且无Kondo共振或Zhang-Rice单态形成，空穴掺杂主要增强Ni-O杂化并减弱关联效应。
摘要：
与铜基超导体相比，无限层镍酸盐（$R$NiO$_2$）表现出一些显著差异，引发了关于稀土离子（$R$=La, Pr, Nd）在低能量多体物理中作用的争论。尽管稀土$4f$轨道在研究中通常被视为惰性“核心”电子，但这一近似已受到质疑。基于与铜酸盐的类比，$4f$态最有可能在PrNiO$_2$中活跃参与，因为Pr铜酸盐与其他铜酸盐差异显著。在此，我们采用密度泛函加动力学平均场理论（DFT+DMFT）研究Pr $4f$轨道的作用，并更广泛地探讨PrNiO$_2$及其空穴掺杂变体的关联电子结构。我们发现Pr $4f$态是绝缘的，且没有Kondo共振或Zhang-Rice单态形成的证据，因为它们在费米能级附近没有任何杂化通道。空穴掺杂的最大影响是将Pr $5d$和$4f$态进一步推离费米能级，同时增强Ni $3d$-O $2p$杂化，从而随着O $2p$态接近费米能级而减弱关联效应。我们再次发现空穴掺杂后$4f$态没有Kondo或Zhang-Rice物理的证据。最后，我们评论了对其他还原价态镍酸盐的启示。
英文摘要：
Infinite-layer nickelates ($R$NiO$_2$) exhibit some distinct differences as compared to cuprate superconductors, leading to a debate concerning the role of rare-earth ions ($R$=La, Pr, Nd) in the low-energy many-body physics. Although rare-earth $4f$ orbitals are typically treated as inert `core' electrons in studies, this approximation has been questioned. An active participation of $4f$ states is most likely for PrNiO$_2$ based on an analogy to cuprates where Pr cuprates differ significantly from other cuprates. Here, we adopt density functional plus dynamical mean field theory (DFT+DMFT) to investigate the role of Pr $4f$ orbitals and more generally the correlated electronic structure of PrNiO$_2$ and its hole-doped variant. We find that the Pr $4f$ states are insulating and show no evidence for either a Kondo resonance or Zhang-Rice singlet formation as they do not have any hybridization channels near the Fermi energy. The biggest effects of hole doping are to shift the Pr $5d$ and $4f$ states further away from the Fermi energy while enhancing the Ni $3d$ - O $2p$ hybridization, thus reducing correlation effects as the O $2p$ states get closer to the Fermi energy. We again find no evidence for either Kondo or Zhang-Rice physics for the $4f$ states upon hole doping. We conclude by commenting on implications for other reduced valence nickelates.
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