Magnon dispersion and anisotropies inSrCu2(BO3)2

Abstract

We study the dispersion of the magnons ͑triplet states͒ in SrCu 2 ͑BO 3 ͒ 2 including all symmetry-allowed Dzyaloshinskii-Moriya interactions ͓J. Phys. Chem. Solids 4, 241 ͑1958͒; Phys. Rev. 120, 91 ͑1960͔͒. We can reduce the complexity of the general Hamiltonian to a simpler form by appropriate rotations of the spin operators. The resulting Hamiltonian is studied by both perturbation theory and exact numerical diagonalization on a 32-site cluster. We argue that the dispersion is dominated by Dzyaloshinskii-Moriya interactions. We point out which combinations of these anisotropies affect the dispersion to linear order, and extract their magnitudes.

Effect of Dzyaloshinskii-Moriya interactions on the phase diagram and magnetic excitations of SrCu2(BO3)Romhányi1, Totsuka2, Penc3 2011Phys. Rev. B

“…Even though they considered a unit cell that has C 4 symmetry, our dispersion agrees with their result, up to ambiguity in the sign in front of the D ′ ||,s in Eq. (35). Furthermore, they extended their analysis by exact diagonalization calculations of the spectra.…”

“…The dispersion in zero field has also been considered by Cheng et al in Ref. [35], where they used a different approach; by suitable rotation of the spin operators they removed the D and arrived at an effective Hamiltonian, where they carried out a first order perturbation expansion to get the dispersions of the effective triplets. Even though they considered a unit cell that has C 4 symmetry, our dispersion agrees with their result, up to ambiguity in the sign in front of the D ′ ||,s in Eq.…”

Hall effect of triplons in a dimerized quantum magnet

“…anisotropies [28][29][30] . Nuclear magnetic resonance measurements also support the presence of DM couplings 31 .…”

Topological triplon modes and bound states in a Shastry–Sutherland magnet

“…Owing to the weak spin-orbit, we a priori expect the hierarchy of energy scales J > D > J zz , J xy . We use the bondoperator formalism 24,25 to represent the two spins of each dimer in terms of singlet and triplet operators,The operators s † and t † α (α = x, y, z) create dimer singlet and triplet states out of the vacuum, respectively, and are subject to the usual hard-core constraint s † s + α t † α t α = 1. The coupling between dimers gives dynamics to the triplon excitations.…”

“…Owing to the weak spin-orbit, we a priori expect the hierarchy of energy scales J > D > J zz , J xy . We use the bondoperator formalism 24,25 to represent the two spins of each dimer in terms of singlet and triplet operators,…”