Combined DFT & STM Study of Fe/Ir(111) Surface States*

Chiral spin structures like those present in Fe/Ir(111) are playing an increasingly important role as processor and device size continue to shrink to length scales where quantum effects are relevant. Here, we present density functional theory (DFT) calculations of the Fe/Ir(111) and Ir(111) surfaces and compare them with experimental scanning tunneling microscopy (STM) images and spectroscopy. We performed our calculations using a fully relativistic projector augmented-wave (PAW) approach in conjunction with spin-orbit coupling (SOC) to produce band structures, surface local density of states (LDOS), and simulated STM topography. Experimental STM studies were performed at low temperature in an ultrahigh vacuum environment. Ir(111) was prepared via Ar sputtering, while a monolayer of Fe was deposited in bare Ir(111) via molecular beam epitaxy (MBE). We find good agreement between our DFT calculations and STM data. Of particular interest is the correspondence in Ir(111)’s surface state at the Γ point. Additionally, we present an analysis of how this state is affected by a pseudomorphic monolayer of Fe.