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 $σ_{1}^{ab}(ω)$, the $c$-axis optical spectra $σ_{1}^{c}(ω)$ exhibit semiconducting behavior. The zero-frequency extrapolation of the optical conductivity $σ_{1}(ω\rightarrow 0) \equiv 1/ρ_{\text{dc}}$ gives a resistivity anisotropy of $ρ_{c}/ρ_{ab} \simeq 366$ 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 $σ_{1}^{ab}(ω)$ and $σ_{1}^{c}(ω)$ 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.

Figures (3)

• Figure 1: (a) Reflectivity of La$_{4}$Ni$_{3}$O$_{10}$ at different temperatures for the $ab$ plane $R^{ab}(\omega)$ and $c$ axis $R^{c}(\omega)$. The inset shows the temperature dependence of $R^{ab}(\omega)$ (red solid circle) and $R^{c}(\omega)$ (blue solid diamond) at $\omega$ = 1000 $\textrm{cm}^{-1}$. (b) The $ab$-plane optical conductivity $\sigma^{ab}_{1}(\omega)$ and $c$-axis optical conductivity $\sigma^{c}_{1}(\omega)$ of La$_{4}$Ni$_{3}$O$_{10}$ at different temperatures. The inset displays $\sigma^{ab}_{1}(\omega)$ and $\sigma^{c}_{1}(\omega)$ at 300 K on the logarithmic scale with the zero-frequency extrapolations being denoted by solid circles. (c) and (d) show $R(\omega)$ and $\sigma_{1}(\omega)$ at 300 K along different directions in a broad frequency range up to 25 000 $\textrm{cm}^{-1}$, respectively.
• Figure 2: (a) The measured $\sigma_{1}^{ab}(\omega)$ at 150 K (cyan solid curve) and the Drude-Lorentz fit (black dashed line). The fit is decomposed into two Drude components D1 (red shaded area), D2 (blue shaded area), and a series of Lorentz components L1$_{ab}$ (green hatched area), L2$_{ab}$ (orange hatched area), L3$_{ab}$ (violet hatched area) and LH$_{ab}$ (grey hatched area). (b) The measured $\sigma_{1}^{c}(\omega)$ at 150 K (cyan solid line) and the fit (black dashed line), which consists of several Lorentz components L1$_{c}$ (green hatched area), L2$_{c}$ (orange hatched area) and LH$_{c}$ (grey hatched area). (c) and (d) show the calculated interband $\sigma_{1}^{ab}(\omega)$ and $\sigma_{1}^{c}(\omega)$, respectively. The vertical dashed lines mark the positions of interband-transition peaks. (e) The calculated electronic band structure of La$_{4}$Ni$_{3}$O$_{10}$, with magenta and navy denoting the Ni-$d_{z^{2}}$ and Ni-$d_{x^{2}-y^{2}}$ orbitals, respectively. Energy- and $\vec{k}$-resolved transition dipole moments for (f) $E \parallel ab$ and (g) $E \parallel c$. The initial and final states are colored with red and blue, respectively.
• Figure 3: The $S$ ratios between different temperatures as a function of $\omega_{c}$ for (a) $E \parallel ab$ and (b) $E \parallel c$. (c)-(h) The $T$ dependence of $S$ (normalized by its value at 300 K) for different cutoff frequencies.