Tuning Kinetic Inductance with Doping in Superconducting Electron Gases at the KTaO₃ (111) Interface

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Information Science

Background:

• Two-dimensional (2D) electron gases (2DEGs) at oxide interfaces are platforms for novel quantum phenomena.
• Superconductivity in 2D systems offers opportunities for fundamental research and device applications.

Purpose of the Study:

• To characterize the sheet kinetic inductance (L_K/□) of the 2D superconductor at KTaO3 (111) interfaces.
• To explore the tunability and temperature dependence of L_K/□.
• To investigate the potential of these materials for superconducting electronics and quantum information science.

Main Methods:

• Fabrication of coplanar waveguide resonators using the 2D superconductor at KTaO3 (111) interfaces.
• Measurement of sheet kinetic inductance (L_K/□) by varying carrier density and temperature.
• Analysis of the temperature dependence of L_K/□ to determine superconducting gap properties.

Main Results:

• Tunable sheet kinetic inductance (L_K/□) from 1.88 to 7.42 nH/□ for critical temperatures (Tc) from 0.62 to 1.81 K.
• L_K/□ values exceeding those of granular aluminum films.
• Temperature dependence consistent with a superconducting gap without nodes.
• Demonstrated robustness of the superconducting state in magnetic fields exceeding 1 Tesla.

Conclusions:

• Superconducting KTaO3 (111) interfacial electron gases exhibit high sheet kinetic inductance and a nodeless superconducting gap.
• The combination of high L_K/□ and high dielectric constant of KTaO3 enables "slow light" resonators with small mode volumes.
• These properties make superconducting KTaO3 (111) interfacial electron gases promising for advanced superconducting electronics and quantum information applications.