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

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

Departamento de Física - Facultad de Ciencias Exactas - Uniersidad Nacional de Buenos Aires

The compound $Ba_3CoSb_2O_9$ is an experimental realization of thetriangular-lattice antiferromagnetic XXZ Heisenberg model. Motivated byrecent neutron scattering experiments that show an unusual extendedcontinuum above the spinwave excitations we investigate the energyspectrum of the modelusing series expansions and mean field Schwinger bosons. The low energy part of the spectrum computed with seriesexpansions gives astrong downward renormalization with respect to linearspin wave theory along with the appearance of rotonic excitations at themiddle edges of the Brillouin zone.