An ab initio study of electron-hole pairs in the insulating single layer cuprates and nickelates

An accurate first-principles treatment of the key ground state properties of correlated materials is a fundamental challenge, and predicting the emergent excited states further increases the complexity. Recently constructed advanced density functionals have proven to be an indispensable tool in addressing the electronic structures of the high temperature superconducting cuprates [1-3] and perovskite iridates [4] at the first-principles level. However, it is unclear if the excited states will be adequately captured within this framework. In this talk, I will highlight our recent work on La$_2$CuO$_4$ and La$_2$NiO$_4$ demonstrating that not only an accurate ground state is possible within a parameter free framework, but also the characteristic behavior of their excitons can be captured in good accord with resonant inelastic X-ray scattering observations [5]. Moreover, by analyzing how the electron and holes form into excitons, we find that the excitons are composed of a linear combination of various prototypical pairing pathways, thereby revealing a multi-orbital nature of the valence states. I will also briefly discuss the implication of these results on the high-Tc pairing mechanism.

[1] J.W. Furness, et al., Nature Communications Physics 1, 11 (2018).
[2] C. Lane, et al., Physical Review B 98, 125140 (2018).
[3] Y. Zhang, et al., Proceedings of the National Academy of Sciences 117, 68 (2020).
[4] C. Lane, et al., Physical Review B 101, 155110 (2020).
[5] C. Lane and J.-X. Zhu, Physical Review B 101, 155135 (2020).