Kitaev Honeycomb Model — Majorana Fermions & Vison Excitations

J_x: 1.0 J_y: 1.0 J_z: 1.0 Flip Bond (create vison pair) Reset Phase: B (gapless Majorana cone)

Kitaev's honeycomb model: spin-1/2 on honeycomb with bond-directional Ising couplings J_x,y,z. Soluble via Majorana fermion representation; visons (Z₂ fluxes) are created in pairs by flipping bonds. The B phase hosts a gapless Majorana cone; A phases are gapped.