Lead


Lay summary
The field of quantum magnetism remain at the forefront of condensed matterphysics. While there are still many unresolved issues even concerning verysimple model systems, the question of what happens when a quantum spinsystem is coupled to a second degree of freedom has so far only beenaddressed in individual cases with few generalized results. In most ofthese studies one degree of freedom was treated perturbatively andintegrated out to give an effective Hamiltonian for the other. It remainsa largely unsolved challenge to treat the two coupled systemssimultaneously, for which few if any general theoretical methods exist. Atpresent we even lack criteria for judging whether secondary degrees offreedom are relevant.Yet, it is becoming increasingly evident that such effects are indeedrelevant if not pivotal to several groups of novel functional materials,such as colossal magneto-resistance in the manganites, decoherence inspin-clusters and possibly the high temperature superconducting cuprates.To address such phenomena in a bottom-up approach, we propose a researchproject, “Vibrating Quantum Magnets”, focusing on the interplay betweenquantum spin systems and lattice degrees of freedom. We shall investigate kandidate materials indicating magnetielastic effectsusing primarily neutron scattering. Neutron scattering has the power toprobe simultaneously magnetic excitations such as spin-waves and latticevibrations, phonons.