Spin-orbit effects in the surface state of Fe(001) revealed by full surface Brillouin zone mapping

The electronic structure of Fe has been experimentally studied using angle-resolved photoemission spectroscopy (ARPES) since the early days of photoemission. Yet, the existence and nature of the Fe(001) surface state remain a subject of ongoing debate. Fe(001) is considered a prototypical transition metal system and moreover, one of the key players in the spintronics research. Here, we present the electronic structure of Fe(001) epitaxially grown on Au(001), mapped by high-resolution ARPES within the entire surface Brillouin zone, to demonstrate for the first time the exact location and extent of the Fe(001) surface state. The experimental results are supported by the relativistic slab calculations performed using density functional theory (DFT). The surface state observed for the pristine Fe(001) surface vanishes after overnight rest of the sample in ultrahigh vacuum as well as after intentional exposure to 5 Langmuir of oxygen which proves that it is not topologically protected. Furthermore, the dispersion of the surface state is found to depend on the relative orientation of the magnetization, which is explained based on the DFT results as related to the Rashba effect. These new experimental and theoretical results contribute to the existing knowledge on the electronic properties of Fe(001) with relevance for the basic research as well as for spintronic effects, such as tunneling anisotropic magnetoresistance.