We have synthesized epitaxial Sr 2 IrO 4 thin-films on various substrates and studied their
electronic structure as a function of lattice-strain. Under tensile (compressive) strain,
increased (decreased) Ir-O-Ir bond-angle is expected to result in increased (decreased)
electronic bandwidth. However, we have observed that the two optical absorption peaks
near 0.5 eV and 1.0 eV are shifted to higher (lower) energies under tensile (compressive)
strain, indicating that the electronic-correlation energy is also affected by in-plane lattice …