Large nanoscale electronic conductivity in complex oxide heterostructures with ultra high electron density

We study the two-dimensional electron gas at the interface of NdTiO₃ and SrTiO₃ to reveal its nanoscale transport properties. At electron densities approaching 10¹⁵ cm^-2, our terahertz spectroscopy data show conductivity levels that are up to six times larger than those extracted from DC electrical measurements. Moreover, the largest conductivity enhancements are observed in samples intentionally grown with larger defect densities. This is a signature of electron transport over the characteristic length-scales typically probed by electrical measurements being significantly affected by scattering by structural defects introduced during growth, and, a trait of a much larger electron mobility at the nanoscale.