Shubnikov-de Hass oscillations to the quantum limit in (111) oriented SrTiO₃ interface 2D electron gas

The (111) surface of perovskite oxide SrTiO₃ has a hexagonal structure, similar to topological insulator Bi₂Se₃. Existence of topological states has been predicted in this system and high mobility two-dimensional (2D) electron gases at interfaces provide a promising platform to study these properties. We created a 2D electron gas at SrTiO3 (111) interfaces with high mobility over 15000 cm²V^-1s^-1 at low temperatures. Utilizing interface engineering, we have achieved relatively low carrier density of 1.3x10¹³ cm^-2. Longitudinal magnetoresistance shows clear Shubnikov-de Hass (SdH) oscillations at low temperatures and high magnetic fields at both 35 T (DC field) and 60 T (pulsed field). In the low carrier density sample, we have observed the lowest Landau level at magnetic field around 20 T, which shifts to higher fields with higher carrier densities. More strikingly, a linear magnetoresistance (LMR) behavior appears at high magnetic field beyond the quantum limit. Temperature and angular dependence of the quantum oscillations as well as the LMR will be discussed.