Raman Characterization of Two-Dimensional Quasiperiodic Antiferromagnets on Various Lattices: Spin-Orbit Mechanism

We study first-order (single-magnon) inelastic light scatterings in spin-$\frac{1}{2}$ two-dimensional quasiperiodic antiferromagnets in comparison with those emergent on periodic lattices. Unlike second-order (two-magnon) Raman scatterings based on an exchange interaction between neighboring spins, the present observations involve an indirect electric-dipole coupling which proceeds through a spin-orbit interaction. We discuss the nearest-neighbor antiferromagnetic XXZ Hamiltonian on various quasiperiodic and periodic bipartite lattices. The first-order spectra, of our present interest, consist only of rotation-invariant and mirror-symmetric magnons, while the second-order ones cannot select any particular magnon. With the exchange anisotropy moving away from the Ising limit toward the Heisenberg isotropic point, every initial delta-function peak bifurcates or divides into more in each individual manner on quasiperiodic lattices, while it remains singly peaked all the way on periodic lattices. Such splittings depend on how many types of isocoordinated sites for each coordination number and relative positions between those of the same type. A perpendicular-space representation of the first-order Raman spectrum serves as a fingerprint of each quasiperiodic tiling.