Composite multi-vortex diffraction-free beams and van-Hove singularities in honeycomb lattices

Area of Science:

• Condensed matter physics
• Photonics
• Materials science

Background:

• Honeycomb optical lattices, such as those in graphene and molybdenum disulfide (MoS2), exhibit unique electronic and optical properties.
• Understanding light propagation in these structured materials is crucial for developing novel photonic devices.

Purpose of the Study:

• To find and characterize diffraction-free beams in graphene and MoS2-type honeycomb optical lattices.
• To analyze the influence of topological charges, valley degrees of freedom, and mass on these beams.
• To investigate the behavior of these beams near the van Hove singularity.

Main Methods:

• Analytical derivation of composite solutions for diffraction-free beams.
• Exact solutions obtained in the Dirac limit for spinor components.
• Analysis of the effects of valley and mass parameters.
• Investigation of beam behavior across the van Hove singularity.

Main Results:

• Diffraction-free beams identified in honeycomb optical lattices, forming multi-vortices with spinor topological charges (n, n±1).
• Exact solutions for spinor components derived in the Dirac limit.
• Valley and mass effects on beam properties analyzed.
• Modification of topological structure near the van Hove singularity observed.
• Beams transform into strongly localized one-dimensional stripes at the singularity.

Conclusions:

• The study presents novel diffraction-free beam solutions for honeycomb optical lattices.
• The findings reveal unique topological properties and transformations of these beams, particularly at the van Hove singularity.
• These results have implications for manipulating light in structured materials and designing advanced photonic systems.