Two dimensional electron gas in the $\delta$-doped iridates with strong spin-orbit coupling: La${}_{\delta }$Sr${}_2$IrO${}_4$

Abstract

Iridates are of considerable current interest because of the strong spin-orbit coupling that leads to a variety of new phenomena. Using density-functional studies, we predict the formation of a spin-orbital entangled two-dimensional electron gas (2DEG) in the $\delta$-doped iridate La${}_{\delta }$Sr${}_2$IrO${}_4$, where a single SrO layer is replaced by a LaO layer. The extra La electron resides close to the $\delta$-doped layer, partially occupying the $J_{\mathrm{eff}}=1/2$ upper Hubbard band and thereby making the interface metallic. The magnetic structure of the bulk is destroyed near the interface, with the Ir${}_0$ layer closest to the interface becoming non-magnetic, while the next layer (Ir${}_1$) continues to maintain the AFM structure of the bulk, but with a reduced magnetic moment. The Fermi surface consists of a hole pocket and an electron pocket, located in two different Ir layers (Ir${}_0$ and Ir${}_1$), with both carriers derived from the $J_{\mathrm{eff}}=1/2$ upper Hubbard band. The presence of both electrons and holes at the $\delta$-doped interface suggests unusual transport properties, leading to possible device applications.