Optical probe of strong correlations in LaNiO$_{3} $ thin films

TL;DR

This study investigates the optical properties of LaNiO₃ thin films, revealing strong electronic correlations that suppress the expected free-carrier response, contrasting with band structure predictions.

Contribution

It provides experimental evidence of strong correlations in LaNiO₃ by optical measurements, challenging conventional band theory predictions.

Findings

Absence of a Drude peak indicating suppressed free carriers

Observation of interband transitions consistent with band calculations

Highlighting the importance of electronic correlations in LaNiO₃

Abstract

The optical properties of LaNiO$_3$ thin films are investigated over a wide energy and temperature range. Thin films of varying thickness were epitaxially grown by pulsed laser deposition on LaAlO$_3$ and SrTiO$_3$ substrates. The optical conductivity data of the films reveal a number of interband transitions above 1 eV which are in good agreement with band structure calculations. No well defined Drude peak is observed however, in stark contrast with LDA theory predicting a finite density of states at the Fermi energy. This experimental finding of a vanishing Drude spectral weight, compared to a finite electron kinetic energy obtained from band structure calculations, highlights the importance of strong electronic correlations in LaNiO$_3$.