$f$-electron and magnetic ordering effects in nickelates LaNiO$_2$ and NdNiO$_2$: remarkable role of the cuprate-like $3d_{x^2-y^2}$ band

Ruiqi Zhang; Christopher Lane; Bahadur Singh; Johannes Nokelainen; Bernardo Barbiellini; Robert S. Markiewicz; Arun Bansil; Jianwei Sun

doi:10.1038/s42005-021-00621-4

arXiv · 2009.05816

$f$-electron and magnetic ordering effects in nickelates LaNiO$_2$ and NdNiO$_2$: remarkable role of the cuprate-like $3d_{x^2-y^2}$ band

Ruiqi Zhang·Christopher Lane·Bahadur Singh·Johannes Nokelainen·Bernardo Barbiellini·Robert S. Markiewicz·Arun Bansil·Jianwei Sun

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Abstract

Recent discovery of superconductivity in the doped infinite-layer nickelates has renewed interest in understanding the nature of high-temperature superconductivity more generally. The low-energy electronic structure of the parent compound NdNiO$_{2}$, the role of electronic correlations in driving superconductivity, and the possible relationship betweeen the cuprates and the nickelates are still open questions. Here, by comparing LaNiO$_2$ and NdNiO$_2$ systematically within a parameter-free density functional framework, all-electron first-principles framework, we reveal the role Nd 4$f$ electrons in shaping the ground state of pristine NdNiO$_2$. Strong similarities are found between the electronic structures of LaNiO$_2$ and NdNiO$_2$, except for the effects of the 4$f$-electrons. Hybridization between the Nd 4$f$ and Ni 3$d$ orbitals is shown to significantly modify the Fermi surfaces of various magnetic states. In contrast, the competition between the magnetically ordered phases depends mainly on the gaps in the Ni $d_{x2-y2}$ band, so that the ground state in LaNiO$_2$ and NdNiO$_2$ turns out to be striking similarity to that of the cuprates. The $d-p$ band-splitting is found to be much larger while the intralayer 3$d$ ion-exchange coupling is smaller in the nickelates compared to the cuprates. Our estimated value of the on-site Hubbard $U$ is similar to that in the cuprates, but the value of the Hund's coupling $J_H$ is found to be sensitive to the Nd magnetic moment. The exchange coupling $J$ in NdNiO$_2$ is only half as large as in the curpates, which may explain why $T_c$ in the nickelates is half as large as the cuprates.

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Ruiqi Zhang, Christopher Lane, Bahadur Singh, Johannes Nokelainen, Bernardo Barbiellini, Robert S. Markiewicz, Arun Bansil, Jianwei Sun. 2020-09-12. $f$-electron and magnetic ordering effects in nickelates LaNiO$_2$ and NdNiO$_2$: remarkable role of the cuprate-like $3d_{x^2-y^2}$ band. https://doi.org/10.1038/s42005-021-00621-4

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