Modulation doping of a Mott quantum well by a proximate polar discontinuity

We present evidence for hole injection into LaAlO(3)/LaVO(3)/LaAlO(3) quantum wells near a polar surface of LaAlO(3) (001). As the surface is brought in proximity to the LaVO(3) layer, an exponential drop in resistance and a decreasing positive Seebeck coefficient are observed below a characteristic coupling length of 10-15 unit cells. We attribute this behavior to a crossover from an atomic reconstruction of the AlO(2)-terminated LaAlO(3) surface to an electronic reconstruction of the vanadium valence. These results suggest a general approach to tunable hole doping in oxide thin-film heterostructures.