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

M. Souri,J. W. Brill,G. Cao,J. Terzic,S. S. A. Seo,J. H. Gruenewald

doi:10.1038/srep25967

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.

Highlights

We have synthesized thermodynamically metastable Ca2IrO4 thin-films on YAlO3 (110) substrates by pulsed laser deposition
It is a formidable task to unveil the physics of layered iridates since only Sr2IrO4 and Ba2IrO4 phases are available for experimental characterizations to date
We report the systematic changes of the structural, transport, and optical properties of layered iridates by investigating meta-stable Ca2IrO4 epitaxial thin-films

Summary

Introduction

We have synthesized thermodynamically metastable Ca2IrO4 thin-films on YAlO3 (110) substrates by pulsed laser deposition. 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. We report the systematic changes of the structural, transport, and optical properties of layered iridates by investigating meta-stable Ca2IrO4 epitaxial thin-films. Investigating Ca2IrO4 in a comparative study with Sr2IrO4 and Ba2IrO4 provides a unique opportunity to explore the layered iridate system, as it allows for the enhancement of the electronic correlation effect (U/W)

Methods

Results

Conclusion