Electrostatic Control of Quantum Phases in KTaO ₃ -Based Planar Constrictions

Two-dimensional electron gases (2DEGs) formed at complex oxide interfaces offer a unique platform to engineer quantum nanostructures. However, the scalable fabrication of devices in these materials remains challenging. Here, we demonstrate an efficient fabrication approach by patterning narrow constrictions in a superconducting KTaO₃-based heterostructure which are individually tunable via coplanar side gates within the 2DEG plane. Leveraging the high dielectric permittivity of KTaO₃, we achieve strong electrostatic modulation of the superconducting 2DEG. Within the superconducting state, we demonstrate efficient modulation of the critical current and Berezinskii-Kosterlitz-Thouless transition temperature at the weak link. Further tuning enables a transition to a dissipative state. All of these states are achievable with a side gate voltage ≲ 1 V. The fabrication process is scalable and versatile, enabling a platform for quantum devices and the study of a wide array of physical phenomena at complex oxide interfaces.