Unique Domain Structure of Two-Dimensional α-Mo2C Superconducting Crystals

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) materials like graphene exhibit properties sensitive to domain boundaries.
• Ultrathin transition metal carbides, including 2D α-Mo2C, are emerging superconducting materials with potential applications.
• The domain structure and boundary effects in these carbides remain largely unexplored.

Purpose of the Study:

• To investigate the microstructure of chemical vapor deposited 2D α-Mo2C crystals.
• To understand the influence of domain boundaries on the superconducting properties of these materials.

Main Methods:

• Atomic-resolution scanning transmission electron microscopy (STEM).
• Large-scale diffraction-filtered imaging.
• Transport studies across domain boundaries.

Main Results:

• Observed uniform Mo atom sublattice but multi-domain C atom sublattices with rotational symmetry in various crystal shapes (except rectangles and octagons).
• Identified well-defined, line-shaped domain boundaries with minimal lattice shear strain.
• Transport measurements revealed broad resistive superconducting transitions with two distinct processes due to localized phase slip events at boundaries.

Conclusions:

• Domain boundaries in 2D α-Mo2C significantly influence superconductivity by inducing localized phase slip events.
• These findings offer new insights into the microstructure of 2D transition metal carbides and the fundamental impact of domain boundaries on 2D superconductivity.