Metallic interfaces in a CaTiO3/LaTiO3 superlattice

Apart from a handful of exceptions, all known complex oxide two-dimensional electron gases (2DEGs) are formed in SrTiO3-based heterostructures, and microscopic information about non-SrTiO3 2DEGs systems is scarce. Here, we report on the realization of metallic conductance in a CaTiO3-based system, CaTiO3/LaTiO3 superlattices, epitaxially grown in a layer-by-layer way on a NdGaO3(110) substrate by pulsed laser deposition. The high quality of the crystal and electronic structures is characterized by in situ reflection high-energy electron diffraction, x-ray diffraction, scanning transmission electron microscopy, and x-ray photoemission spectroscopy. Electrical transport confirms the formation of metallic interfaces in the CaTiO3/LaTiO3 superlattice. In addition, Hall measurements reveal that in the CaTiO3/LaTiO3 superlattice the room-temperature carrier mobility is nearly three times higher than that of the CaTiO3/YTiO3 superlattice, implying the importance of TiO6 octahedral tilts and rotations on the carrier mobility of a 2DEG. Since doped CaTiO3 is an A-site polar metal, our results provide a materials system for designing synthetic two-dimensional polar metals.