EPSCoR Research Fellows: NSF: Neutron Scattering Experiments on Magnetic Weyl Semimetals

Recent developments in neutron scattering data collection and analysis can lead to new scientific opportunities at the latest generation neutron sources such as the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). These facilities harness modern computing power to collect data using a paradigm called “event mode” detection. When a neutron is scattered from a sample into a detector, each neutron is recorded individually along with all information about the detection. This proposal is to send PI William Gannon and a University of Kentucky (UK) graduate student to ORNL to work closely with Dr. Christina Hoffmann to learn the intricacies of event mode analysis. Due to the complexity of the data, this can only be done in close collaboration with experts such as Dr. Hoffmann. We will analyze our existing neutron diffraction data sets on proposed magnetic Weyl semimetal materials using event mode information as a prelude to conduct future neutron diffraction experiments to exploit event mode data, extracting more information about our materials. We furth propose to build a probe to apply an electric field at cryogenic temperatures to samples in neutron scattering experiments to continuously tune the Fermi level and observe how ordered magnetic states in Weyl materials are affected by the changing field, an experiment that can only be done with event mode data analysis. The knowledge and analysis techniques gained from this fellowship will inform all future neutron scattering experiments carried out in the Gannon lab. Intellectual Merit Appreciation for the role of topology in condensed matter physics has led to an explosion of interest in materials that host protected electronic states due to their potential for use in next generation technologies. Considerable recent interest has centered on Weyl semimetals. Weyl semimetals are naturally conductors in their bulk, allowing exploitation of both their protected surface states – where information could be encoded and transmitted without fear of loss – and more conventional bulk conducting states. This proposal seeks to increase the information that can be taken from neutron scattering experiments on the crystalline and magnetic properties of such materials by taking advantage of the event mode data generated at state-of-the-art neutron sources such as the SNS. We also propose to construct a probe to take advantage of these capabilities by continuously changing electric fields in a neutron scattering experiment at cryogenic temperatures. Broader Impacts Novel correlated electron states such as those studied in this proposal have the potential to make a sea change in future technologies. However, the state of Kentucky is historically underserved in science and engineering education for most students and is not well positioned to participate in the future workforce that will shape these technologies. As the flagship research university in Kentucky, UK is uniquely suited to help alleviate the problems caused by this issue as two thirds of the student enrollment is from Kentucky. As science and technology literacy are increasingly important in all aspects of life, a lack of people with training is a pressing issue in the state. The state-of-the-art analysis and probe construction proposed here directly addresses these shortcomings. -This proposal aligns with the National Science Foundation, Directorate of Mathematical and Physical Sciences (MPS), Division of Materials Research (DMR), Condensed Matter Physics (CMP). -The proposed host site is Oak Ridge National Laboratory in Oak Ridge, TN. The primary research collaborator is Dr. Christina Hoffmann.