Abstract
Based on first-principles calculations in the framework of van der Waals density functional
theory, we find that giant, Rashba-like spin splittings can be induced in both the surface
states and quantum well states of thin Bi2Se3 films by application of an external electric field.
The charge is redistributed so that the Dirac cones of the upper and lower surfaces become
nondegenerate and completely gapless. Interestingly, a momentum-dependent spin texture is
developed on the two surfaces of the films. Some of the quantum well states, which reside in
the middle of the Bi2Se3 film under zero field, are driven to the surface by the electric field.
The Rashba splitting energy has a highly non-linear dependence on the momentum and the
electric field due to the large contribution of the high-order Rashba terms, which suggests
complex spin dynamics in the thin films of Bi2Se3 under an electric field.
