Electronically driven superconductor insulator transition in   electrostatically doped La$_{2}$CuO$_{4+\delta}$ thin films
  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. 
J. Garcia-Barriocanal, A. Kobrinskii, X. Leng, J. Kinney, B. Yang, S.   Snyder, A. M Goldman
cond-mat.supr-con