Gate-tunable superconductivity and nanoscale constrictions in ionic liquid gated SrTiO₃

SrTiO₃, a perovskite oxide, is an excellent candidate for gate-tunable superconducting devices due to the dilute nature of its superconductivity and its high dielectric constant. In this work, we used ionic liquid gating to accumulate a two-dimensional electron gas (2DEG) patterned into gated nanoscale constrictions (0.3 - 1 µm wide). The distinctive feature of this study was the use of a patterned 2DEG (rather than metals) to define side gate contacts. This enhances gate capacitances and simplifies the lithography process, enabling more complex gate geometries.

We tuned the constriction conductance from full pinch-off up to 6 e²/h, allowing the constriction to function as a tunable coupler between adjacent 2DEG reservoirs. A global ionic liquid gate modulated the constriction leads between a uniform superconducting state and a metallic state with incoherent superconducting puddles.

These results demonstrate a viable route towards complex gate architectures necessary to develop superconducting SrTiO₃ 2DEGs into a platform for topological or spin qubits.