  We report on an extraordinary field effect of the superconducting
LaAlO3/KTaO3(111) interface with Tc ~2 K. By applying a gate voltage (VG)
across KTaO3, the interface can be continuously tuned from superconducting into
insulating states, yielding a dome-shaped Tc-VG dependence. The electric gating
has only a minor effect on carrier density as evidenced in the Hall-effect
measurement, while it changes spatial profile of the carriers in the interface,
hence the carrier's disorder level significantly. As temperature is decreased,
the resistance saturates at lowest temperature in both superconducting and
insulating sides, despite an initial dramatic dropping or increasing, which
suggests an emergence of quantum metallic state associated with failed
superconductor and/or fragile insulator. A VG-modulation of the
magnetic-field-driven superconductor to insulator quantum phase transition
reveals a non-universal criticality.
