Low-Energy Charge Dynamics in Dirac Fermion Materials

University Of California-Riverside, Riverside CA

Investigators

Abstract

Technical Abstract: The objective of this project is to better understand the exotic change dynamics in materials with a Dirac point close to the Fermi energy in their band structure. The classic example is graphene; however, topological insulators, which are bulk insulators, also have Dirac fermions in unique metallic chiral edge states. Despite numerous theoretical and experimental papers on this topic, several issues are still unresolved regarding the low-frequency conductivity, the importance of quasiparticle interactions and the role of impurities and defects in their electronic properties. Terahertz time-domain spectroscopy will be used to investigate the response of these materials in this previously unexplored frequency range. Along with important fundamental issues, these materials have the potential for new technological functionality from high-performance electronic devices to topological quantum computing. Understanding the charge dynamics at terahertz frequencies is a crucial component for pursuing some of these applications. Finally, this project will train two graduate students and postdoc in a quickly emerging area of nanoscience. UCR runs a Summer Bridge to Research program that supports summer research for undergraduates in STEM fields who are Hispanic and/or come from low-income families. Each summer, a student in this program will participate on this project. Non-Technical Abstract: As a result of their unique structure, Dirac fermion materials, such as graphene and topological insulators, have exotic electronic properties and display a wide range of fascinating phenomena, which is the reason they have attracted an enormous amount of interest. Fundamentally related to their properties is the response of the electrons to external electric fields. The objective of this project is to investigate this response at terahertz frequencies using time-domain spectroscopy. This type of an investigation in a previously unexplored frequency range is relevant to resolving several issues related to how the electrons interact with defects and with each other. These materials have the potential for new technological functionality from high-performance electronic devices to topological quantum computing. In addition to advancing our fundamental understanding, knowledge of the electron?s response at these frequencies is important for pursuing some of these new applications. Finally, this project will train two graduate students and postdoc in a quickly emerging area of nanoscience. UCR runs a Summer Bridge to Research program that supports summer research for undergraduates in STEM fields who are Hispanic and/or come from low-income families. Each summer, a student in this program will participate on this project.