Hole doping dependent electronic instability and electron-phonon coupling in infinite-layer nickelates

Abstract

Recently, charge density waves (CDWs) have been observed in $\mathrm{CaCu}{\mathrm{O}}_{2}\text{\ensuremath{-}}\mathrm{analogous}$ infinite-layer nickelates $R\mathrm{Ni}{\mathrm{O}}_{2}$ ($R=\mathrm{La}$, Nd) but exhibit very different hole doping dependent behaviors compared to that in cuprates, raising a challenging question on its origin. In this paper, employing density functional theory, many-body dynamic mean field theory, and determinant quantum Monte Carlo calculations, we propose a synergetic contribution from both electronic instability (EI) and moment-dependent electron-phonon coupling (MEPC). Unexpectedly, the EI and MEPC are mainly contributed by Ni $3{d}_{x2\ensuremath{-}y2}$ and $R 5{d}_{z2}$, highlighting the unique multiorbital feature. Interestingly, a strong Fermi surface nesting (FSN) induced by the unique feature of van Hove singularity (VHS) across the Fermi level exists in $R\mathrm{Ni}{\mathrm{O}}_{2}$, which is sensitive to hole doping. The hole doping can rapidly reduce FSN of Ni $3{d}_{x2\ensuremath{-}y2}$ by shifting VHS and decrease the occupation of $R 5{d}_{z2}$, which can largely weaken EI and MEPC in $R\mathrm{Ni}{\mathrm{O}}_{2}$. Remarkably, the temperature-insensitive feature of EI and MEPC could be a hint for rather high-temperature CDWs observed in undoped $R\mathrm{Ni}{\mathrm{O}}_{2}$. Our theory may offer one possible explanation to the experimentally observed CDW formation and its hole-doping dependence in nickelates, and also establishes a unified understanding of the hole doping dependent EI and MEPC in nickelates and cuprates.