Energy spectrum and low temperature entropy of the spin1/2 triangular antiferromagnet

A. MEZIO; C. N. SPOSETTI; L.O. MANUEL; A. E. TRUMPER

Bariloche

Conferencia; International Conference on Recent Progress in Many-Body Theories; 2011

Centro Atómico Bariloche

We present results of the dynamical structure factor for the spin1/2 triangular Heisenberg model, recently computed by us, using the mean field Schwingerboson theory [1]. We find that a reconstructed dispersion, resulting from a non trivial redistribution of the spectral weight, agrees quite well with the spinexcitation spectrum found with series expansions [2]. In particular, we recover the strong renormalization with respect to linear spin wave theory along with theappearance of rotonlikeminima at the midpoints of edges of the hexagonal Brillouin zone. By computing the densitydensitydynamical structure factor, weidentify an unphysical weak signal of the spin excitation spectrum with the relaxation of the local constraint of the Schwinger bosons assumed at the mean fieldlevel. Finally, by selecting appropriately the physical spin excitations, we show that within the context of the present bosonic spinon theory, the high values ofentropy found at low temperatures with series expansion can be explained due to the presence of the roton excitations [3].