4π-Periodic Supercurrent from Surface States in Cd_{3}As_{2} Nanowire-Based Josephson Junctions

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Superconductivity and surface states in Dirac semimetals can lead to exotic phenomena like 4π-periodic supercurrent.
• Distinguishing 4π-periodic supercurrent from conventional 2π-periodic Josephson effects is crucial but challenging due to overlapping signatures, such as suppressed Shapiro steps.

Purpose of the Study:

• To experimentally differentiate the signature of 4π-periodic supercurrent from the ordinary Josephson effect in Nb-Dirac semimetal Cd$_{3}$As$_{2}$ nanowire-Nb junctions.
• To identify unambiguous evidence for the 4π-periodic supercurrent by analyzing radio frequency (RF) irradiation effects.

Main Methods:

• Fabrication of Nb-Cd$_{3}$As$_{2}$ nanowire-Nb Josephson junctions.
• Radio frequency (RF) irradiation measurements with continuous power dependence at various frequencies.
• Analysis of Shapiro step behavior, particularly the n=1 step and the presence of nodes.

Main Results:

• Observed suppression of the n=1 Shapiro step, a known characteristic that can also occur in conventional Josephson junctions.
• Uncovered a residual supercurrent at the n=0 step, identified as a direct and predominant signature of the 4π-periodic supercurrent.
• Demonstrated gate voltage tunability of surface/bulk contributions and the visibility of the n=1 step.

Conclusions:

• The residual supercurrent at the n=0 step provides definitive evidence for the 4π-periodic supercurrent in Dirac semimetal Josephson junctions.
• The study offers critical insights for exploring topological superconductivity in Dirac semimetals.
• Gate-tunable control over surface and bulk states opens avenues for manipulating topological superconducting properties.