The proposed project deals with high-resolution measurements of the lifetime of magnetic excitations in simple (quantum) magnets and of lattice vibrations (phonons) in the nominally well-understood simple-metal superconductors. The results will be compared with model calculations, which are density functional theory (DFT) calculations for phonons, and concepts beyond linear spin wave theory for quantum magnets. The results will be essential for the understanding of basic notions in quantum effects in magnetism, as well as in the foundations of superconductivity in simple metals.
Essential for the detailed comparison between experiment and model is the development and verification of software that fully accounts for the experimental (four-dimensional) resolution function in momentum and energy. This resolution, in turn, must be combined with third party code for modelling excitation spectra. This forms the instrumental technique development component of this project, where the developed software will be highly beneficial for users of the chopper spectrometers at ISIS and elsewhere, and in particular relevant to spectrometers that are under construction at the European Spallation Source (ESS) in Sweden.