Shubnikov-de Haas Oscillations in LaTiO$_3$/SrTiO$_3$ Heterostructures

Emergent metallic behavior in heterostructures of the Mott insulator LaTiO$_3$ and the band insulator SrTiO$_3$ was observed for the first time more than a decade ago. It has often been compared to other oxide systems which have a two-dimensional Fermi surface, but there have been few studies probing the dimensionality of the metallicity in this system. We have studied the transport properties of thin films of LaTiO$_3$ on SrTiO$_3$ substrates. Our measurements have indicated that the entirety of the LaTiO$_3$ film is conductive with an additional contribution near the interface. When the film thickness is on the order of 3-4 unit cells, we observe two sets of Shubnikov-de Haas oscillations - low frequency oscillations with a frequency of 2T and high frequency of 36T. We attribute the observation of these two sets of oscillations to a Rashba splitting which creates a smaller inner Fermi pocket and a larger outer Fermi pocket. These results are consistent with our measurements of in plane anisotropic magnetoresistance and a weak antilocalization correction to the magnetoconductance Further measurements on the angular dependence of the oscillations indicate that their frequency does not change, thus indicating that the Fermi surface is more three-dimensional.