Excitaciones magnéticas en el modelo XXZ antiferromagnético triangular

GHIOLDI, E. A.; A. MEZIO; L.O. MANUEL; A. E. TRUMPER

Bariloche

Congreso; Reunion Nacional de Fisica; 2013

Asociacion Fisica Argentina

The compound Ba_3CoSb_2O_9 is an experimental realization of the triangular-lattice antiferromagnetic XXZ Heisenberg model. Motivated by recent neutron scattering experiments that show an unusual extended continuum above the spin wave excitations we investigate the energy spectrum of the model using series expansions and mean field Schwinger bosons. The low energy part of the spectrum computed with series expansions gives a strong downward renormalization with respect to linear spin wave theory along with the appearance of rotonic excitations at the middle edges of the Brillouin zone. These excitations, already found in the isotropic case J_z/J=1, persist for all values of anisotropy 0