A two-dimensional tunable double Weyl fermion in BL-α borophene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid-State Physics

Background:

• Two-dimensional (2D) materials with nontrivial band crossings, such as linear or double Weyl points, are of significant research interest.
• Identifying existing 2D materials exhibiting these exotic electronic states remains a considerable challenge.

Purpose of the Study:

• To discover and characterize a novel 2D material hosting tunable nontrivial band crossings.
• To investigate the electronic properties and strain-dependent behavior of Weyl points in BL-α borophene.

Main Methods:

• First-principles calculations
• Symmetry analysis
• Band structure analysis
• Strain engineering

Main Results:

• Discovery of BL-α borophene as a metal with a tunable double Weyl point.
• Observation of anisotropic band dispersion and strain-induced band bending in the double Weyl point.
• Demonstration of transformation of double Weyl points into Weyl points and linear Weyl points under different strain conditions.
• Identification of a Weyl complex case with both double Weyl and linear Weyl points.

Conclusions:

• BL-α borophene is identified as a viable existing 2D material for the experimental study of nontrivial band crossings.
• The tunable nature of Weyl points in BL-α borophene under strain offers opportunities for controlling its electronic properties.