Geminal Mirror Twin Boundaries in H-Phase NbTe₂

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Grain boundaries (GBs) in transition metal dichalcogenides (TMDs) critically affect their properties.
• Mirror twin boundaries (MTBs) exhibit unique quantum phenomena like topological states and charge density waves.
• Large-scale, well-aligned MTB fabrication is a significant challenge.

Purpose of the Study:

• To present a facile solution method for fabricating high-density paired MTBs in monolayer 1H-NbTe₂.
• To characterize the atomic structure and formation mechanism of these MTBs.
• To explore the implications of paired MTBs for quantum device applications.

Main Methods:

• Solution-based synthesis of monolayer 1H-NbTe₂.
• Atomic-resolution scanning transmission electron microscopy (STEM) for structural identification.
• Density functional theory (DFT) calculations for mechanism and property analysis.

Main Results:

• Successfully introduced high-density, aligned paired MTBs with quantized spacings in 1H-NbTe₂.
• Identified two distinct MTB types: Nb-oriented 4|4E and Te-oriented 4|4P.
• Hypothesized a formation mechanism involving intralayer atomic rearrangements and H-phase coalescence.
• DFT confirmed stabilization of metastable H-phase, enabling superconductivity and nontrivial band topology.

Conclusions:

• The developed method advances boundary engineering in TMDs.
• Paired MTBs offer a pathway for designing novel quantum devices.
• This work facilitates the control of quantum properties through engineered grain boundaries.