Three-dimensional character of the Fermi surface in ultrathin ${\mathrm{LaTiO}}_3/{\mathrm{SrTiO}}_3$ heterostructures

${\mathrm{LaTiO}}_3$ films on ${\mathrm{SrTiO}}_3$ single crystal substrates exhibit metallic behavior attributed to the ${\mathrm{LaTiO}}_3$ film, the interface as well as part of the ${\mathrm{SrTiO}}_3$. In the limit of ultrathin ${\mathrm{LaTiO}}_3$ films on ${\mathrm{SrTiO}}_3$, the contribution to the metallicity from strain-induced electronic structure modification of the ${\mathrm{LaTiO}}_3$ film is minimized so that the dominant contribution to metallicity is from the interface and part of the ${\mathrm{SrTiO}}_3$ due to charge transfer of $3d$ electrons from ${\mathrm{LaTiO}}_3$ to ${\mathrm{SrTiO}}_3$. In such a limit, we observe quantum oscillations whose angular dependence indicates a three-dimensional Fermi surface. Such angular dependence is observed in two sets of quantum oscillations—one low frequency and one high frequency—that we have attributed to an inner and outer Fermi surface associated with a Rashba-like spin split hybridized $d_{xz+yz}$ band.

Figure 1

Angular dependence of the low frequency oscillations. The angle of the magnetic field is measured with respect to the normal of the interface. Red circles indicate the extrema used to calculate the frequency.

Figure 2

Angular dependence of the high frequency oscillation. The given angle is measured from the normal of the interface. Red circles indicate the extrema used to calculate the frequency.

Figure 3

Angular dependence of the Fermi surface area determined from the frequency of the oscillations. The circles represent the experimental data and the solid lines show the prediction from the tight binding model.

Figure 4

Diagram of the proposed Fermi pocket. There is a cut through the outer Fermi pocket in order to visualize the smaller inner pocket.