Tuning the electronic structure of Sr2IrO4 thin films by bulk electronic doping using molecular beam epitaxy

TL;DR

This study demonstrates how bulk electronic doping via molecular beam epitaxy can effectively modify the electronic structure of Sr2IrO4 thin films, revealing shifts in Fermi level and emergence of electron pockets, with implications for tuning their properties.

Contribution

It introduces a novel doping method using molecular beam epitaxy to control the electronic structure of Sr2IrO4 thin films, showing effects on Fermi level and electronic states.

Findings

Fermi level shifts upward with increased doping

Emergence of electron pocket at M point at 15% doping

Doping suppresses insulating behavior but retains low-temperature localization

Abstract

By means of oxide molecular beam epitaxy with shutter-growth mode, we have fabricated a series of electron-doped (Sr1-xLax)2IrO4(001)(x = 0, 0.05, 0.1 and 0.15) single crystalline thin films and then investigated the doping dependence of electronic structure utilizing in-situ angle-resolved photoemission spectroscopy. We find that with increasing doping proportion, the Fermi levels of samples progressively shift upward. Prominently, an extra electron pocket crossing the Fermi level around the M point has been evidently observed in 15 % nominal doping sample. Moreover, bulk-sensitive transport measurements confirm that doping effectively suppresses the insulating state with respect to the as-grown Sr2IrO4, though 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.