Development and Application of beta-detected NMR to Quantum Materials and Beyond

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The high energy particles emitted in radioactive decay are very easy to detect, a property that enables *radiotracer* techniques that follow a radiolabeled species through chemical, physical or biological processes, forming the basis for powerful medical imaging techniques like Positron Emission Tomography (PET scans). Certain types of radioactivity can, however, report much more than just the radiolabel's location: they sense the electromagnetic characteristics of its local atomic environment. The most important example is radioactive beta decay, used in beta-detected nuclear magnetic resonance (ßNMR) that is the basis of this proposal. ßNMR radioisotopes must have very short half-lives on the order of seconds or less, so they are made immediately before use. The ISAC facility at TRIUMF, Canada's particle accelerator centre, located at UBC in Vancouver, provides short-lived radioisotopes as ion beams. Mainly we use the isotope 8Li (halflife 0.848 seconds). Only a few other labs can make such beams, but more are being constructed. Our efforts lead the world in the development of ßNMR. With its new ARIEL project, a new source of 8Li will be available in 2021, dramatically increasing the amount of time available for these experiments. A key strength of ion-implanted ßNMR is the ability to adjust the depth of the probe in a material. While there are many powerful surface-sensitive methods to study the topmost atomic layer, there are very few that reveal properties as a function of depth below a surface. Our main motive is to study surface and interface effects that give rise to poorly understood depth-dependent phenomena in solids on depth scales of a few nanometers (1 billionth of a meter) to a few hundred nm, an important range for modern electronics. Material interfaces, like metal/semiconductor, metal/polymer or electrode/electrolyte are crucial to many devices. As devices are miniaturized towards *nanotechnology*, every atom is near an interface. However, interface effects are not well understood. This proposal aims to study interface problems using the depth-resolved power of ßNMR. We will study new materials that will be the basis for new technologies, e.g. solid state electrolytes for Li+ batteries, correlated electronic conductors and topological materials with unique electromagnetic properties that may be used to sidestep limitations of conventional materials. We will study nanostructured glassy polymers to understand the effect of structure on molecular dynamics, and we will extend the application of ßNMR to new areas such as biochemistry. Canada will benefit by leading the world in advanced materials research with outcomes that result in a better fundamental understanding of material interfaces, enabling optimization of current technologies and engineering radically new ones.