Off-equilibrium study of the fluctuation-dissipation relation in the easy-axis Heisenberg antiferromagnet on the kagomé lattice

Violation of the fluctuation-dissipation theorem (FDT) in a frustrated Heisenberg model on the kagome lattice is investigated using Monte Carlo simulations. The model exhibits glassy behavior at low temperatures accompanied by very slow dynamics. Both the spin-spin autocorrelation function and the response to an external magnetic field are studied. Clear evidence of a constant value of the fluctuation-dissipation ratio and long-range memory effects is observed in this model. The breakdown of the FDT in the glassy phase follows the predictions of mean-field theory for spin glasses with one-step replica symmetry breaking.