Induced Topological Superconductivity in a BiSbTeSe₂-Based Josephson Junction.

Area of Science:

• Condensed Matter Physics
• Quantum Materials
• Superconductivity

Background:

• Josephson junctions exhibit supercurrent flow, typically with 2π periodicity.
• Majorana bound states are exotic quasiparticles predicted to exist in topological superconductors.
• A 4π-periodic supercurrent is a signature characteristic of Majorana bound states.

Purpose of the Study:

• To investigate the radio frequency response of Josephson junctions for evidence of 4π-periodic supercurrent.
• To establish a protocol for detecting Majorana bound states via supercurrent analysis.
• To report the observation of 4π-periodic supercurrent in specific material systems.

Main Methods:

• Systematic study of radio frequency response across various temperatures and frequencies.
• Fabrication and characterization of BiSbTeSe2-based Josephson junctions.
• Analysis of Shapiro step behavior under radio frequency irradiation.

Main Results:

• Observed an absence of the first Shapiro step in response to radio frequency irradiation.
• Detected a 4π-periodic contribution to the supercurrent in BiSbTeSe2 Josephson junctions.
• Found qualitative agreement with a theoretical model incorporating a 4π-periodic supercurrent component at high irradiation power.

Conclusions:

• The study successfully demonstrates a method for probing 4π-periodic supercurrents.
• The findings provide experimental evidence for Majorana bound states in BiSbTeSe2 Josephson junctions.
• This work opens avenues for utilizing Josephson junctions in topological quantum computing applications.