Spin dynamics in pressure-induced magnetically-ordered phases in PHCC

We present inelastic neutron scattering experiments on the $S=1/2$ frustrated gapped quantum magnet piperazinium hexachlorodicuprate under applied hydrostatic pressure. These results show that at 9 kbar the magnetic triplet excitations in the system are gapless, contrary to what was previously reported. We show that the changes in the excitation spectrum can be primarily attributed to the change in a single exchange pathway.