A test of the bosonic spinon hypothesis for the triangular antiferromagnet

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

Buenos Aires. Argentina

Workshop; At the Frontiers of Condensed Matter V; 2010

Centro Atomico Constituyentes

We show that the anomalous excitation spectrum of the spin-1/2 triangularHeisenberg model, recently found with series expansion by Zheng et al.[Phys. Rev. Lett. 96, 057201 (2006)] , can be naturally interpreted in termsof spinon excitations using a Schwinger boson mean field theory. Inparticular, we find a qualitative and quantitative agreement of the  strongrenormalization of the high energy part of the spectrum with respect to spinwave results along with the appearance of roton like minima at the midpointsof faces of the hexagonal Brillouin zone. By looking at the dominant part oflow energy peaks of the dynamical structure factor the roton like minima canbe traced back to the crossing of the spinon branches shifted by Q/2 , whereQ = (4/3, 0) is the magnetic wave vector of the 120 Neel order. We also findthat near the location of the roton minima the contribution of the twospinon continuum to the static structure factor is about 40% of the totalweight. The implications of our findings are contrasted with recentcalculations within the context of 1/s spin wave expansions.