Optical and Magnetic Spectroscopy of Carbon-Based Materials

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****NON-TECHNICAL ABSTRACT****This individual investigator award supports a research project that aims to deepen our understanding of carbon networks, a class of emerging materials with potential to create revolutionary multifunctional electronics. Carbon networks, including graphene and carbon nanotubes, are predicted to have fascinating electronic, optical and magnetic properties, where small changes in atomic arrangements can dramatically alter their behavior. As progress in this field moves forward, researchers need increasingly creative tools to study the electronic properties of carbon nanomaterials. This work leverages methods pioneered by the PI to use magnetism as a non-invasive probe of electronic properties. As an example, disorder in planar networks of carbon is currently of great interest because such regions appear to couple to light and may also be useful in 'steering' electrons around in carbon devices. Dramatic changes in magnetic properties induced by disorder (caused by oxygen bonding to the network) have already been observed and provide an incisive tool for relating disorder to changes in the electronic landscape of these materials. This research will involve graduate students in collaborative work that will help them chart successful interdisciplinary careers. Support for this project will enable an expansion of outreach activities at an NSF funded Shared Equipment Facility (SEF), providing additional remote experiments and recruitment of new users. ****TECHNICAL ABSTRACT****This individual investigator project will study fundamental optical and magnetic properties of materials derived from hexagonal networks of carbon, including graphene, graphene oxide, and carbon nanotubes. Much of this research exploits important connections between orbital diamagnetism and local optical and transport properties. Specifically, the former provides a complementary probe of single-particle electronics that can often clarify the latter. In graphene oxide, changes in orbital diamagnetism will quantify aromatic network disruption that may hold a key to bandgap engineering and optical emission in that material. In the case of carbon nanotubes, a battery of highly purified samples will be used to understand how diamagnetism in carbon nanotubes depends on symmetry and atomic structure. For graphene, the possibility of magnetic anomalies that arise from quantum criticality at the Dirac point will be investigated. In addition, a unique collection of purified carbon nanotube samples will be used to provide a definitive map of carbon nanotube dark exciton energies as a function of atomic structure. This research will involve graduate students in collaborative work that will help them chart successful careers. Support for this project will enable an expansion of outreach activities at an NSF funded Shared Equipment Facility (SEF), providing additional remote experiments and recruitment of new users.