Energy spectrum of the triangular XXZ Heisenberg Model Realized in $Ba_3CoSb_2O_9$

GHIOLDI, ESTEBAN A.; MEZIO, ALEJANDRO; MANUEL, LUIS O.; SINGH, RAJIV R. P.; OITMAA, JAN; TRUMPER, ADOLFO E.

Ciudad Autónoma de Buenos Aires - FCE

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

Departamento de Física - FCE - UBA

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 spinwave excitations we investigate the energy spectrum of the modelusing series expansions and mean field Schwinger bosons. The low energy part of the spectrum computed with series expansions gives astrong 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 range $0