  The oxide interface between LaAlO3 and KTaO3(111) can host an electron gas
that condenses into superconductivity at low temperatures. In this work, we
demonstrate a local and non-volatile control of this electron gas using a
biased conducting atomic force microscope tip. By scanning the tip, charges can
be accumulated on the surface of LaAlO3, which subsequently tune the conduction
of the buried LaAlO3/KTaO3(111) interface largely, varying from conducting
(superconducting) to insulating states. The tuning effects are stable for > 20
h at room temperature. The maximum modulation of carrier density is > 8 times
10^13/cm^2. This result suggests a new model system in which rewritable
superconducting, normal, and insulating states can be flexibly defined in the
same material on demand.
