Abstract
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 Hc=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 et al., Phys. Rev. Lett. 96, 047210 2006 is found to shift from hc0,35 at HHC to hc=0.25 for HHC. A drastic reduction of magnon bandwidths in
the ordered phase Garlea et al., 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.
