title: High-energy magnon dispersion and multimagnon continuum in the two-dimensional Heisenberg antiferromagnet.
abstract: We use quantum Monte Carlo simulations and numerical analytic continuation to study high-energy spin excitations in the two-dimensional S = 1/2 Heisenberg antiferromagnet at low temperature. We present results for both the transverse (x) and longitudinal (z) dynamic spin structure factors Sx,z(q,omega) at q = (pi,0) and (pi/2, pi/2). Linear spin-wave theory predicts no dispersion on the line connecting these momenta. Our calculations show that in fact the magnon energy at (pi,0) is 10% lower than at (pi/2, pi/2). We also discuss the transverse and longitudinal multimagnon continua and their relevance to neutron scattering experiments.
authors.affiliation: Department of Physics, University of Illinois at Urbana-Champaign, 61801, USA.
authors.forename: A W
authors.initials: AW
authors.lastname: Sandvik
authors.forename: R R
authors.initials: RR
authors.lastname: Singh