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

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.