Charge-stripe Fluctuations in Nd$_{4}$Ni$_{3}$O$_{8}$ as Evidenced by Optical Spectroscopy

TL;DR

This study uses optical spectroscopy to reveal charge-stripe fluctuations in Nd$_{4}$Ni$_{3}$O$_{8}$, showing temperature-dependent spectral weight behavior indicative of strong electronic correlations.

Contribution

It provides experimental evidence of charge-stripe fluctuations in Nd$_{4}$Ni$_{3}$O$_{8}$ through optical spectroscopy and compares findings with theoretical calculations and other nickelates.

Findings

Charge-stripe fluctuations are evidenced by optical conductivity features.

The $eta$ band relates to electronic transitions across fluctuating charge stripes.

Spectral weight follows a $T^{2}$ law, indicating strong correlation effects.

Abstract

We present an investigation into the optical properties of Nd$_{4}$Ni$_{3}$O$_{8}$ at different temperatures from 300 down to 5~K over a broad frequency range. The optical conductivity at 5~K is decomposed into IR-active phonons, a far-infrared band $\alpha$, a mid-infrared band $\beta$, and a high-energy absorption edge. By comparing the measured optical conductivity to first-principles calculations and the optical response of other nickelates, we find that Nd$_{4}$Ni$_{3}$O$_{8}$ features evident charge-stripe fluctuations. The $\beta$ band is attributed to electronic transitions between the gapped Ni-$d_{x^2-y^2}$ bands due to fluctuating charge stripes, while the high-frequency absorption edge corresponds to the onset of transitions involving other high-energy bands. Furthermore, an analysis of the temperature-dependent optical spectral weight reveals a $T^{2}$ law, which is likely to originate from strong correlation effects.