Electric field control of superconductivity at the LaAlO ₃ /KTaO ₃ (111) interface

Abstract

The oxide interface between LaAlO₃ and KTaO₃(111) can harbor a superconducting state. We report that by applying a gate voltage (<i>V</i> _G) across KTaO₃, the interface can be continuously tuned from superconducting into insulating states, yielding a dome-shaped <i>T</i> _c-<i>V</i> _G dependence, where <i>T</i> _c is the transition temperature. The electric gating has only a minor effect on carrier density but a strong one on mobility. We interpret the tuning of mobility in terms of change in the spatial profile of the carriers in the interface and hence, effective disorder. As the temperature is decreased, the resistance saturates at the lowest temperature on both superconducting and insulating sides, suggesting the emergence of a quantum metallic state associated with a failed superconductor and/or fragile insulator.