Theory of the SrTiO3 surface state two-dimensional electron gas

We present a theory of the quasi-two-dimensional electron gas (2DEG) systems that appear near the surface of SrTiO3 when a large external electric field attracts carriers to the surface. We find that nonlinear and nonlocal screening by the strongly polarizable SrTiO3 lattice plays an essential role in determining 2DEG properties. The electronic structure always includes weakly bound bulklike bands that extend over many SrTiO3 layers. At 2D carrier densities exceeding similar to 10(14) cm(-2), tightly bound bands emerge that are confined within a few layers of the surface.