Inelastic Spectroscopies of The Physics of Quantum Spin Liquid Materials

Quantum spin liquids (QSL's) are novel states of matter possessing long range quantum entanglement. Inelastic spectroscopies are the preeminent tool for exploring their rich physics. An important experimental signature of such novel phases is the presence of spin excitations characterized by fractionalized quantum numbers. For the kagome quantum spin liquid candidate materials Zn-barlowite and herbertsmithite, our inelastic scattering measurements (using both neutron and x-ray probes) provide evidence for fractionalized spinon excitations. Furthermore, experiments on closely related materials with competing states allow us to determine the most important magnetic interactions and to identify signatures of broken symmetry states. In addition, our high energy resolution studies shed light on the role that impurities play in the QSL ground state physics. We discuss the implications our recent experimental investigations of the spin excitations which span low energies (~J/100) to high energies (~10J) on our powder and single crystal samples of QSL and related materials.