Meron Spin Textures in Momentum Space.

Area of Science:

• Condensed matter physics
• Photonics
• Topological physics

Background:

• Topological spin textures are crucial in condensed matter physics.
• Previous studies have not observed meron spin textures in photonic systems.
• Photonic crystals offer a tunable platform for exploring exotic phenomena.

Purpose of the Study:

• To demonstrate the generation of momentum-space meron spin textures in free-space electromagnetic fields.
• To investigate the role of Berry curvature in photonic crystals for creating these textures.
• To explore the potential applications of these textures in manipulating light polarization.

Main Methods:

• Utilizing a photonic crystal slab with nonzero Berry curvature.
• Breaking the inversion symmetry of a honeycomb photonic crystal to gap Dirac cones.
• Analyzing the pseudospin textures of photonic bands near the band gap.
• Observing the manifestation of pseudospin textures in leakage radiation polarization.

Main Results:

• Successfully generated momentum-space meron and antimeron spin textures.
• These textures were observed in photonic bands near gapped Dirac cones.
• The pseudospin textures directly mapped to the spin texture of leakage radiation.
• Demonstrated a direct visualization of local Berry curvature.

Conclusions:

• Photonic crystal structures enable the creation of novel topological spin textures.
• The observed meron spin textures in momentum space are a new phenomenon in both electronic and photonic systems.
• This work opens avenues for robust manipulation of light polarization and modal characteristics using topological concepts.