Highly Anisotropic Charge Dynamics and Spectral Weight Redistribution in the Trilayer Nickelate La${}_4$Ni${}_3$O${}_{10}$

Abstract

We study the $ab$-plane and $c$-axis charge dynamics of La${}_4$Ni${}_3$O${}_{10}$ using optical spectroscopy. While a pronounced Drude profile, i.e. metallic response, is observed in the $ab$-plane optical conductivity ${\sigma }_1^{ab}(\omega )$, the $c$-axis optical spectra ${\sigma }_1^c(\omega )$ exhibit semiconducting behavior. The zero-frequency extrapolation of the optical conductivity ${\sigma }_1(\omega \to 0)\equiv 1/{\rho }_{\text{dc}}$ gives a resistivity anisotropy of ${\rho }_c/{\rho }_{ab}\simeq 366$ at 300~K for La${}_4$Ni${}_3$O${}_{10}$, which is much larger than the values in iron-based superconductors but comparable to those in high-$T_c$ cuprates. The interband response is also highly anisotropic, showing salient orbital selectivity for light polarized in the $ab$ plane and along the $c$ axis. The interband-transition peaks in both ${\sigma }_1^{ab}(\omega )$ and ${\sigma }_1^c(\omega )$ are located at lower energies compared to density-functional-theory predictions, signifying considerable electronic correlations. By investigating the spectral weight transfer, we find that in the pristine phase, Coulomb correlations have a marked impact on the charge dynamics of \LNO, whereas in the density-wave state, a gap opens with the Ni-$d_{z^2}$ orbital being involved.

8 pages, 3 figures. Comments are welcome and appreciated