Spectral signatures of magnon interactions in antiferromagnets in high fields*

In this talk I will discuss signatures of interactions between magnons that show up in the dynamical spin correlations of antiferromagnets in presence of a magnetic field, focusing on the high magnetization regime. I will first present our results for the antiferromagnetic spin-1/2 chain, where we uncover the appearance of two-magnon bound states in the transverse dynamical susceptibility. This bound state feature generalizes the one arising from string states in the Bethe ansatz solution of the integrable case. I will then address higher-dimensional systems and argue that these observations are not unique to 1D.