Scanning tunneling spectroscopy of a dilute two-dimensional electron system exhibiting Rashba spin splitting

Using scanning tunneling spectroscopy (STS) at 5 K in B fields up to 7 T, we investigate the local density of states of a two-dimensional electron system (2DES) created by Cs adsorption on p-type InSb (110). The 2DES, which in contrast to previous STS studies exhibits a 2D Fermi level, shows standing waves at B = 0 T with corrugations decreasing with energy and with wave numbers in accordance with theory. In magnetic field percolating drift states are observed within the disorder broadened Landau levels. Due to the large electric field perpendicular to the surface, a beating pattern of the Landau levels is found and explained quantitatively by Rashba spin splitting within the lowest 2DES subband. The Rashba splitting does not contribute significantly to the standing wave patterns in accordance with theory.