Polarization and Electric Field Dependence of Electronic Properties in LaAlO₃/SrTiO₃ Heterostructures

We have done the detailed theoretical investigation by performing calculations for numerous LaAlO(3)/SrTiO(3) heterostructures using the generalized gradient approximation. We find that external electric field can cooperate or compete with spontaneous polarization and effectively modulate band dispersion around the Fermi level. Positive field can induce a reversible insulator-metal transition in insulating heterostructures. Rather than the Ti-d(xy) interface state that emerges in insulator-metal transition without external field, the pd-σ anti-bonding state composed of the O-p(z) and the Ti-d(3z(2)-1) at SrTiO(3) surface exchanges its hole with the electron of the O-p(x),p(y) orbitals (bonding states) at LaAlO(3) surface with the presence of positive field. Associated with insulator-metal transition, there is a remarkable change of local work functions in heterostructure, which suggests that LaAlO(3)/SrTiO(3) heterostructures are the promising candidates for novel nanoscale oxide electronic devices and technology, for instance, the Schottky diodes with adjustable barrier height.