1D quantum magnets: magnons, correlations, and entanglement
Magnon Dispersion E(k)
Heisenberg Hamiltonian: H = J Σ (SᵢˣSᵢ₊₁ˣ + SᵢʸSᵢ₊₁ʸ + ΔSᵢᶻSᵢ₊₁ᶻ).
For J > 0 (antiferromagnetic) and Δ = 1 (isotropic), the model is exactly solvable via Bethe Ansatz.
Magnons are spin-wave quasiparticles with dispersion E(k) = J(cos k − cos π) for the ferromagnetic case.