Tuning the Electronic Structure of Sr₂IrO₄ Thin Films by Bulk Electronic Doping Using Molecular Beam Epitaxy

By means of oxide molecular beam epitaxy with shutter-growth mode, we fabricate a series of electron-doped (Sr_1?xLa_x)₂IrO₄ (001) (x=0, 0.05, 0.1 and 0.15) single crystalline thin films and then investigate the doping dependence of the electronic structure utilizing in-situ angle-resolved photoemission spectroscopy. It is found that with the increasing doping content, the Fermi levels of samples progressively shift upward. Prominently, an extra electron pocket crossing the Fermi level around the M point is evidently observed in the 15% nominal doping sample. Moreover, bulk-sensitive transport measurements confirm that the doping effectively suppresses the insulating state with respect to the as-grown Sr₂IrO₄, though the doped samples still remain insulating at low temperatures due to the localization effect possibly stemming from disorders including oxygen deficiencies. Our work provides another feasible doping method to tune electronic structure of Sr₂IrO₄.