Nanoscale NMR Studies of Topological Insulators, Crystalline Insulators and Dirac Semimetals
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Abstract
In recent years the emergence of gapless topologically protected edge states in the solid state has led to searches for new phases of condensed matter in new and existing materials. For example, some thermoelectrics and Kondo insulators have been shown to be topological insulators. The protected edge states in topological insulators are due to the combination of spin-orbit coupling and time-reversal invariance. Examples of exotic phenomena include the quantum anomalous Hall effect, fractional quantum anomalous Hall effect, topological superconductor, fractional time-reversal invariance, topological Kondo insulator, topological crystalline insulator and the topological magneto-electric effect. However, interesting properties of topological materials are found at edges and interfaces, making them challenging to study from the experimental standpoint. In this talk, we will review recent advances in experimental techniques to study the electronic and magnetic properties of such topological materials. Among the novel techniques, we shall discuss radioactive ion beam spectroscopy and nuclear magnetic resonance. Our group has been carrying out experiments at TRIUMF using low energy spin-polarized lithium-8 ion beams to resolve properties as function of depth, with nanoscale resolution. Such studies reveal substantial modulations of the metallic character of these materials at those length scales. Studies of material defects in the bulk will also be discussed. Ultimately, the development of new experimental methods is expected to lead to not only insight for improving material properties but may also enable the development of composite materials with optimized properties.
Bio
Dr. Bouchard obtained a bachelor's degree in physics and business management from McGill University in Montréal, Canada, a Master's degree in medical biophysics from the University of Toronto and a Ph.D. in Chemistry from Princeton University. His doctoral dissertation explores the use of multiple quantum coherence and long-range dipolar interactions in condensed matter to characterize heterogeneous material microstructure. During his stay in the laboratory of Alex Pines at the University of California, Berkeley he developed novel approaches and methodologies to portable, low-field NMR and MRI, microfluidics and hyperpolarization methods to the study of chemical reactions. He joined the UCLA faculty during the summer of 2008 to pursue research in physical chemistry.
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Physics, Room 203, Purdue University, West Lafayette, IN