Improving the Josephson energy in high-Tc superconducting junctions for ultra-fast electronics

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Josephson tunnel junctions are crucial components in superconducting electronics.
• High-temperature superconductors offer potential advantages in device operation.
• Controlling insulating barriers is key to optimizing Josephson junction performance.

Purpose of the Study:

• To investigate the electrical transport properties of vertically-stacked Josephson tunnel junctions.
• To evaluate the performance of strontium titanate (SrTiO3) as an insulating barrier in these junctions.
• To determine the feasibility of using high-temperature superconductors in such devices.

Main Methods:

• Fabrication of Josephson tunnel junctions using 16 nm thick Gadolinium Barium Copper Oxide (GdBa2Cu3O7-δ) electrodes.
• Utilized 1-4 nm thick strontium titanate (SrTiO3) as the insulating barrier material.
• Electrical transport measurements, including Fraunhofer pattern analysis, were performed at 12 K.

Main Results:

• Successful Josephson coupling was achieved for junctions with 1 nm and 2 nm SrTiO3 barriers.
• Obtained Josephson energies of 3.1 mV (1 nm STO) and 5.7 mV (2 nm STO) at 12 K after subtracting residual current.
• Residual current in Fraunhofer patterns suggests potential contributions from pinholes and thickness fluctuations in the SrTiO3 barrier.

Conclusions:

• The observed Josephson coupling demonstrates the viability of SrTiO3 as an effective insulating barrier in high-temperature superconductor Josephson junctions.
• The obtained Josephson energies are promising for developing superconducting devices with reduced thermal noise and higher operating frequencies.
• Further optimization of barrier uniformity is recommended to fully realize the potential of these devices.