Parallel electron-hole bilayer conductivity from electronic interface reconstruction: Experiment

Electronic reconstruction at polar interfaces is the change in electronic properties to compensate an otherwise diverging electric potential. For the perovskite oxide SrTiO$_3$-LaAlO$_3 $ model system we show that an additional capping SrTiO$_3$ layer prevents structural or chemical reconstruction at the LaAlO$_3$ surface and provides a possibility to accommodate holes. Magnetotransport, scanning tunneling microscopy and in situ ultraviolet photoelectron spectroscopy provide evidence for electronic reconstruction and for the presence of two spatially separated sheets with electron and hole carriers, that are as close as 1 nm, forming an excitingly versatile system to realize and study 2D excitonic phenomena.