  Despite several attempts, the intimate electronic structure of
two-dimensional electron systems buried at the interface between LaAlO3 and
SrTiO3 still remains to be experimentally revealed. Here, we investigate the
transport properties of a high-mobility quasi-two-dimensional electron gas at
this interface under high magnetic field (55 T) and provide new insights for
electronic band structure by analyzing the Shubnikov-de Haas oscillations.
Interestingly, the quantum oscillations are not 1/B-periodic and produce a
highly non-linear Landau plot (Landau level index versus 1/B). Among possible
scenarios, the Roth-Gao-Niu equation provides a natural explanation for
1/B-aperiodic oscillations in relation with the magnetic response functions of
the system. Overall, the magneto-transport data are discussed in light of
high-resolution scanning transmission electron microscopy analysis of the
interface as well as calculations from density functional theory.
