Energy spectrum of the triangular XXZ Heisenberg model realized in Ba3CoSb2O9

A. E. TRUMPER; GHIOLDI, ESTEBAN; A. MEZIO; L. O. MANUEL; R. P. P. SINGH; J. OITMAA

Buenos Aires

Conferencia; 27th International Conference on Low Temperature Physics; 2014

Universidad de Buenos Aires

The compound Ba3CoSb2O9 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 Jz/J=1, persist for all values of anisotropy range 0