Tunable superconducting diode effect in a topological nano-SQUID

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Electronics

Background:

• Josephson diodes exhibit one-way current flow without resistance, but achieving large, tunable effects has been challenging.
• Existing platforms for Josephson diodes have limitations in performance and controllability.

Purpose of the Study:

• To engineer a novel device exhibiting a large and tunable Josephson diode effect.
• To investigate the underlying physics of this diode effect in a topological insulator system.

Main Methods:

• Fabrication of a lateral Josephson junction using a topological-insulator (TI) nanowire side-contacted by superconductors.
• Application of a parallel magnetic field and back-gate voltage to tune the diode properties.
• Modeling the system as a nano-superconducting quantum interference device (SQUID) to explain the observed effects.

Main Results:

• A large Josephson diode effect with efficiency reaching 0.3 was achieved in the TI nanowire device.
• The diode's magnitude and sign were tunable via magnetic field and back-gate voltage.
• The observed effect was modeled successfully as a SQUID, indicating topological superconductivity.

Conclusions:

• The developed TI nanowire Josephson junction demonstrates a significant and tunable Josephson diode effect.
• The findings suggest the emergence of topological superconductivity in these systems.
• This work opens new avenues for superconducting electronics and quantum devices.