Correlation of Dirac ordering with optical activity in AlB₂-type Dirac MBenes

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Chemistry

Background:

• Two-dimensional (2D) materials like graphene exhibit unique electronic properties due to Dirac cones.
• AlB2-type MBenes are an emerging class of 2D materials with potential for advanced applications.
• Understanding their electronic and optical behavior is crucial for material design.

Purpose of the Study:

• To systematically investigate the electronic properties and optical activity of AlB2-type Dirac MBenes.
• To explore the correlations between electronic structure, stability, and optical behavior.
• To assess their potential for optoelectronic and photovoltaic applications.

Main Methods:

• First-principles calculations were employed to study electronic dispersions and optical properties.
• Phonon-spectral calculations and ab initio molecular dynamics simulations confirmed thermal and dynamic stability.
• Analysis of exciton binding energies and dielectric constants provided insights into electron-hole screening.

Main Results:

• All investigated Dirac MBenes exhibit finitely gapped Dirac cones, except FeB2MBene which is a semimetal.
• The emergence of Dirac cones is attributed to the interplay of metal and boron atomic orbitals.
• Exciton binding energies align with the 2D Mott-Wannier model, indicating Mott-Wannier exciton characteristics.
• Significant light absorption was observed in the NIR and visible regions.

Conclusions:

• AlB2-type Dirac MBenes are thermally and dynamically stable 2D materials with tunable electronic and optical properties.
• The presence of a band gap in Dirac cones is beneficial for optoelectronic applications.
• These materials show promise for optoelectronics and photovoltaics due to their light absorption and exciton behavior.
• Control over d-state electrons and doping can modulate exciton characteristics.