  Using an electronic double layer transistor we have systematically studied
the superconductor to insulator transition in La$_{2}$CuO$_{4+\delta}$ thin
films growth by ozone assisted molecular beam epitaxy. We have confirmed the
high crystalline quality of the cuprate films and have demonstrated the
suitability of the electronic double layer technique to continuously vary the
charge density in a system that is otherwise characterized by the presence of
miscibility gaps. The transport and magneto-transport results highlight the
role of electron-electron interactions in the mechanism of the transition due
to the proximity of the Mott insulating state.
