Superconductor-insulator transition in long MoGe nanowires

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Superconducting properties are influenced by physical processes at various length scales.
• Understanding the critical regime in one-dimensional superconductors is crucial for device applications.

Purpose of the Study:

• To identify the dominant physical process in the critical regime of one-dimensional superconducting wires.
• To investigate the factors controlling the superconductor-insulator transition (SIT) in narrow MoGe wires.

Main Methods:

• Fabrication of very narrow (9-20 nm) MoGe wires using electron-beam lithography.
• Systematic study of transport properties across a wide range of wire lengths (1-25 μm).
• Application of external magnetic fields to induce transitions.

Main Results:

• Observed a superconductor-insulator transition (SIT) controlled by the wire's cross-sectional area and potentially its width-to-thickness ratio.
• Found that the mean-field critical temperature decreases exponentially with the inverse of the wire's cross section.
• Demonstrated that a similar SIT can be induced by an external magnetic field.
• Identified some long superconducting MoGe nanowires exhibiting localized superconductivity where localization length is smaller than wire length.

Conclusions:

• The observed SIT in narrow MoGe wires is not explained by current theories.
• Wire dimensions and magnetic fields are key parameters controlling the SIT.
• Localization effects play a significant role in the behavior of long superconducting nanowires.