Electronic excitations and structure of Li2IrO3 thin films grown on ZrO$_{2}$:Y (001) substrates

TL;DR

This study reports the growth, structural characterization, and optical and electronic properties of Li2IrO3 thin films on ZrO2:Y substrates, revealing insights into their excitations and potential for exotic ground states.

Contribution

It presents the first pulsed laser deposition of Li2IrO3 films with detailed structural and optical analysis, advancing understanding of iridate thin films for quantum materials.

Findings

Films exhibit preferential crystalline orientations.

Resistivity follows a 3D variable range hopping mechanism.

Optical gap of approximately 300 meV and in-gap excitations identified.

Abstract

Thin films are a prerequisite for application of the emergent exotic ground states in iridates that result from the interplay of strong spin-orbit coupling and electronic correlations. We report on pulsed laser deposition of Li$_{2}$IrO$_{3}$ films on ZrO$_{2}$:Y(001) single crystalline substrates. X-ray diffraction confirms preferential (001) and (10-1) out-of-plane crystalline orientations with well defined in-plane orientation. Resistivity between 35 and 300 K is dominated by a three-dimensional variable range hopping mechanism. The dielectric function is determined by means of spectroscopic ellipsometry and, complemented by Fourier transform infrared transmission spectroscopy, reveals a small optical gap of $\approx$ 300 meV, a splitting of the $5d$-$t_{2g}$ manifold, and several in-gap excitations attributed to phonons and possibly magnons.