Investigations of metastable Ca2IrO4 epitaxial thin-films: systematic comparison with Sr2IrO4 and Ba2IrO4

TL;DR

This study successfully synthesized metastable Ca2IrO4 thin-films, revealing electronic similarities to related iridates but with a larger energy gap, demonstrating the potential of epitaxial stabilization for exploring complex oxides.

Contribution

It presents the first epitaxial growth of metastable Ca2IrO4 thin-films and compares their electronic properties with Sr2IrO4 and Ba2IrO4.

Findings

Ca2IrO4 thin-films have similar electronic structure to Sr2IrO4 and Ba2IrO4

The energy gap in Ca2IrO4 is larger due to increased octahedral tilting

Epitaxial stabilization enables exploration of metastable layered iridates

Abstract

We have synthesized thermodynamically metastable Ca2IrO4 thin-films on YAlO3 (110) substrates by pulsed laser deposition. The epitaxial Ca2IrO4 thin-films are of K2NiF4-type tetragonal structure. Transport and optical spectroscopy measurements indicate that the electronic structure of the Ca2IrO4 thin-films is similar to that of Jeff = 1/2 spin-orbit-coupled Mott insulator Sr2IrO4 and Ba2IrO4, with the exception of an increased gap energy. The gap increase is to be expected in Ca2IrO4 due to its increased octahedral rotation and tilting, which results in enhanced electron-correlation, U/W. Our results suggest that the epitaxial stabilization growth of metastable-phase thin-films can be used effectively for investigating layered iridates and various complex-oxide systems.