Twisted van der Waals Josephson Junction Based on a High-T_c Superconductor

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Stacking 2D van der Waals (vdW) materials at relative twist angles enables twistronics.
• Anisotropic layered materials offer high tunability for exotic quantum phenomena.
• Understanding anisotropic superconducting properties is crucial for novel electronic devices.

Purpose of the Study:

• To investigate anisotropic superconducting order parameters in twisted Bismuth-2212 (Bi-2212) vdW junctions.
• To explore the effect of twist angle on Josephson coupling in Bi-2212 vdW junctions.
• To develop a fabrication technique for vdW-based twistronics platforms.

Main Methods:

• Fabrication of atomically clean vdW interfaces using the microcleave-and-stack technique.
• Creation of twisted Bi-2212 vdW junctions with varying twist angles (0°, 45°, 90°).
• Measurement of Josephson coupling and comparison with theoretical models.

Main Results:

• Maximum Josephson coupling observed at 0° and 90° twist angles, comparable to intrinsic Josephson junctions.
• Suppression of Josephson coupling as twist angle approaches 45°, disappearing completely at 45°.
• Quantitative agreement between experimental results and theoretical calculations incorporating d-wave superconductivity and tunneling incoherence.

Conclusions:

• The study reveals the anisotropic nature of superconducting order parameters in Bi-2212.
• The twist angle dependence of Josephson coupling is directly linked to the material's intrinsic anisotropy.
• A novel, air-compatible fabrication technique for vdW twistronics platforms was demonstrated.