  Herein, we reported giant tunability of the physical properties of 2DEGs at
the spinel/perovskite interface of {\gamma}-Al2O3/SrTiO3 (GAO/STO). By
modulating the carrier density thus the band filling with ionic-liquid gating,
the system experiences a Lifshitz transition at a critical carrier density of
3E13 cm-2, where a remarkably strong enhancement of Rashba spin-orbit
interaction and an emergence of Kondo effect at low temperatures are observed.
Moreover, as the carrier concentration depletes with decreasing gating voltage,
the electron mobility is enhanced by more than 6 times in magnitude, leading to
the observation of clear quantum oscillations. The great tunability of GAO/STO
interface by EDLT gating not only shows promise for design of oxide devices
with on-demand properties, but also sheds new light on the electronic structure
of 2DEG at the non-isostructural spinel/perovskite interface.
