CAREER: A platform for broadband terahertz spectroscopy of 2D materials and heterostructures

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Non-technical AbstractMethods used in investigating properties of nanoscale materials is fundamentally restricted by what is called the diffraction limit. This limit constrains the size of a material under investigation to roughly the wavelength of the radiation used to probe it. This project uses terahertz radiation with wavelengths of hundreds of micrometers to probe the emerging two-dimensional materials that have unique and unprecedented properties including superconductivity and magnetism. By confining the terahertz radiation to the surface of the small-scale materials being studied, this technique circumvents the diffraction limit and offers new understanding about the dynamic response and electronic properties of these fascinating materials. The research also advances understanding of high frequency radiation transmission on small-scale chips for applications in next generation high frequency communications technology. The project heavily relies on undergraduate and graduate student involvement and provides an outlet for these students to learn cutting-edge experimental techniques. Several activities in this project focus on recruitment and retention of underrepresented students for long term careers in science. This project is jointly funded by the Division of Materials Research (DMR) and the Established Program to Stimulate Competitive Research (EPSCoR).Technical AbstractTerahertz (THz) time domain spectroscopy has led to a deeper understanding of the properties of matter and has become an invaluable tool in the study of low energy physics and dynamics in materials. The THz spectrum resides in a range of energies and timescales which are particularly important in materials with strong interactions. It would be highly advantageous to apply the technique to the emerging class of correlated two-dimensional, van der Waals heterostructures to characterize ground states and interactions which are currently not well understood. This project designs and optimizes a platform for THz spectroscopy of microscopic materials, at first focusing on 2D superconductors and magnets. Using planar waveguides and optically pumped photoconductive switches, the technique harnesses on-chip single cycle THz pulses to perform THz time domain spectroscopy of these materials, ushering in spectral information of low energy excitations and dynamics. The platform provides much needed insight on the possible pairing mechanisms in unconventional 2D superconductors and the relaxation dynamics of 2D magnets. It can also be readily applied to microscopic materials beyond investigations here and has broad application in routes to optimization of sub-diffraction THz spectroscopy and high frequency communications. This project is jointly funded by the Division of Materials Research (DMR) and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.