Dynamical structure factor of frustrated spin models: a variational Monte Carlo approach

The spin dynamical structure factor is computed within a variational framework to study frustrated Heisenberg models in one and two dimensions. Within this approach, the relevant part of the spectrum is approximated by considering two-spinon excitations over the best variational Ansatz for the ground-state wave function. A benchmark of this approach on the one-dimensional J₁-J₂ model give an excellent description of both the gapless and gapped (dimerized) phases, also describing the incommensurate structure for large frustrating ratios J₂/J₁. In the square lattice, we are able to unveil the dynamical signatures of the transition between the Neel and the (gapless) spin-liquid phases that takes place for J₂/J₁=0.45.