First-principles density functional calculations demonstrate that a spin-polarized two-dimensional conducting state can be realized at the interface between two nonmagnetic band insulators. The (001) surface of the diamagnetic insulator ${\mathrm{FeS}}_2$ (pyrite) supports a localized surface state deriving from Fe $d$ orbitals near the conduction band minimum. The deposition of a few unit cells of the polar perovskite oxide ${\mathrm{LaAlO}}_3$ leads to electron transfer into these surface bands, thereby creating a conducting interface. The occupation of these narrow bands leads to an exchange splitting between the spin subbands, yielding a highly spin-polarized conducting state distinct from the rest of the nonmagnetic, insulating bulk. Such an interface presents intriguing possibilities for spintronics applications.

• Received 29 June 2011

DOI:https://doi.org/10.1103/PhysRevLett.107.166601