Electric--field effect on electron-doped infinite-layer Sr${}_{0.88}$La${}_{0.12}$CuO${}_{2+x}$ thin films

We have used the electric–field effect to modulate the resistivity of the surface of underdoped Sr${}_{0.88}$La${}_{0.12}$CuO${}_{2+x}$ thin films, allowing opposite modifications of the electron and hole density in the CuO${}_2$ planes, an original situation with respect to conventional chemical doping in electron-doped materials. When the Hall effect indicates a large contribution of a hole band, the electric–field effect on the normal state resistivity is however dominated by the electrons, and the superconducting transition temperature increases when carriers are transfered from holes to electrons.