Giant Rashba splitting originating from the broken symmetry at surfaces

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Peculiar Rashba effects, such as giant spin splitting, on low-dimensional nano-structures, which are formed on semiconductor surfaces, have been investigated both experimentally and theoretically. We observed extraordinary Rashba effects like Rashba spin that is 100 % spin polarized and points along the surface normal direction, and Rashba splitting at a point without time-reversal symmetry, which was believed to be a necessary condition for this effect. These extraordinary effects are concluded to result from the symmetry of the surface. We also showed that the sign of the Rashba splitting is determined by the particular charge asymmetry near the atomic cores.