Superconductor to Non-Superconductor Transitions at Oxide Interface Tuned by Electrostatic Dual Gates

The quantum phase transitions from superconductor to non-superconductor in two dimensions (2D) are determined by various factors including carrier density, disorder, and dissipation coupling. By applying a dual gate technique on the LaAlO$_{3}$/SrTiO$_{3}$ interface superconductor, we obtained the degrees of freedom to tune these factors and induce different phase transitions electrostatically. Our device is formed by simultaneous gating from the top of the epitaxially grown LaAlO$_{3}$ and the back of the SrTiO$_{3}$ (100) substrate. The structural asymmetry of the dual gate device and the large and nonlinear dielectric constant of SrTiO$_{3}$ enable independent and wide-range parameter tuning. We found, by top gating, a superconductor-metal transition can be achieved within the highly conducting limit ($k_{F}l $\textgreater \textgreater 1, where $k_{F}$ is the Fermi wave vector and $l$ is the electron mean free path). By back gating, a superconductor-insulator transition can be observed with the collapse of $k_{F}l$. Our results provide a comprehensive perspective for the quantum phase transitions for the oxide interface systems.