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.

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Published in Scientific Reports, v. 6, article no. 25967, p. 1-5.

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We acknowledge the support of National Science Foundation grants DMR-1454200 (for thin-film synthesis and characterizations), DMR-1265162 (for target synthesis), and DMR-1262261 (for infrared spectroscopy) in addition to a grant from the Kentucky Science and Engineering Foundation as per Grant Agreement #KSEF-148-502-14-328 with the Kentucky Science and Technology Corporation.