Dynamics of quantum spin liquid and spin solid phases in IPA-CuCl3 under an applied magnetic field studied with neutron scattering

Inelastic and elastic neutron scattering is used to study spin correlations in the quasi-one-dimensional quantum antiferromagnet IPA-CuCl3 in strong applied magnetic fields. A condensation of magnons and commensurate transverse long-range ordering is observe at a critical field H-c=9.5 T. The field dependencies of the energies and polarizations of all magnon branches are investigated both below and above the transition point. Their dispersion is measured across the entire one-dimensional Brillouin zone in magnetic fields up to 14 T. The critical wave vector of magnon spectrum truncation [Masuda , Phys. Rev. Lett. 96, 047210 (2006)] is found to shift from h(c)approximate to 0.35 at H < H-c to h(c)=0.25 for H>H-c. A drastic reduction of magnon bandwidths in the ordered phase [Garlea , Phys. Rev. Lett. 98, 167202 (2007)] is observed and studied in detail. New features of the spectrum, presumably related to this bandwidth collapse, are observed just above the transition field.