Electrical properties and subband occupancy at the (La, Sr)(Al, Ta)O3/SrTiO3 interface

The quasi-two-dimensional electron gas at oxide interfaces provides a platform for investigating quantum phenomena in strongly correlated electronic systems. Here, we study the transport properties at the high-mobility (La0.3Sr0.7) (Al0.65Ta0.35) O3/SrTiO3 interface. Before oxygen annealing, the as-grown interface exhibits a high electron density and electron occupancy of two subbands: higher-mobility electrons (μ1≈10^4 cm2 V−1s−1 at 2 K) occupy the lower-energy 3dxy subband, while lower-mobility electrons (μ1≈103cm2V−1s−1 at 2 K) propagate in the higher-energy 3dxz/yz-dominated subband. After removing oxygen vacancies by annealing in oxygen, only a single type of 3dxy electrons remain at the annealed interface, showing tunable Shubnikov–de Haas oscillations below 9 T at 2 K and an effective mass of 0.7me. By contrast, no oscillation is observed at the as-grown interface even when electron mobility is increased to 50 000 cm2V−1s−1 by gating voltage. Our results reveal the important roles of both carrier mobility and subband occupancy in tuning the quantum transport at oxide interfaces.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore)Published versio