Epitaxy-distorted spin-orbit Mott insulator in Sr2IrO4 thin films

TL;DR

This study demonstrates how epitaxial strain in Sr2IrO4 thin films influences their structural, electronic, and magnetic properties, revealing strain-induced modifications in tetragonality, electronic anisotropy, and charge gap, thus enabling functional control of spin-orbit Mott insulators.

Contribution

It shows that epitaxial strain can be used to manipulate the structural and electronic properties of Sr2IrO4 thin films, providing a new approach for tuning spin-orbit Mott systems.

Findings

Tensile strain reduces tetragonality by 1.2%.

Linear dichroism decreases with increased strain.

Charge gap decreases from 200 meV to 50 meV.

Abstract

High quality epitaxial thin films of Jeff=1/2 Mott insulator Sr2IrO4 with increasing in-plane tensile strain have been grown on top of SrTiO3(001) substrates. Increasing the in-plane tensile strain up to ~0.3% was observed to drop the c/a tetragonality by 1.2 %. X-ray absorption spectroscopy detected a strong reduction of the linear dichroism upon increasing in-plane tensile strain towards a reduced anisotropy in the local electronic structure. While the most relaxed thin film shows a consistent dependence with previously reported single crystal bulk measurements, electrical transport reveals a charge gap reduction from 200 meV down to 50 meV for the thinnest and most epitaxy-distorted film. We argue that the reduced tetragonality plays a major role in the change of the electronic structure, which is reflected in the change of the transport properties. Our work opens the possibility for exploiting epitaxial strain as a tool for both structural and functional manipulation of spin-orbit Mott systems.