CAREER: vdW isotope heterostructuring showcased in phononic light-matter interactions

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Nontechnical Description:Element isotopes are atoms with distinct masses since they have the same number of protons but differ in the number of neutrons in the nuclei. Isotopes exist in all forms of materials and devices and therefore are an important governing factor for material properties. This CAREER project aims to develop an innovative method to modify fundamental material responses by making nanometer-scale multilayer structures with unique arrangements of various isotopes. The principal investigator showcases this method in controlling the vibrations of atoms and atomic planes as well as their interactions with light. The new material responses demonstrated in this project can be used for a broad range of applications, including microscopy, computer memory, and biomedical treatment. In addition, this project offers excellent training opportunities for undergraduate and graduate students, especially the underrepresented minorities, on experiments and simulations of light and waves at the nanoscale, and nanomaterial fabrication. The planned outreach and summer research activities can provide K-12 students and high-school teachers with hands-on research experience and teaching units for their curriculum.Technical Description:The primary goal of this project is to explore unprecedented material properties by engineering the constituent element isotopes in van der Waals heterostructures. The principal investigator plans to build van der Waals heterostructures comprised of various monoisotopic components by the state-of-the-art van der Waals assembly technique, in order to establish advances over current isotope-homogenous material systems. Scanning probe nano-imaging, nano-spectroscopy, and Raman spectroscopy are used to investigate propagating phonon polaritons, phonon dynamics, and interlayer phonons in these heterostructures. In addition, finite element method electromagnetics simulation and density functional material theory are planned for a thorough understanding of the experimental observations. These efforts can reveal unique electromagnetic wave behaviors, dynamic tunability, and memory effects for phononic light-matter interactions. The prototype heterostructures demonstrated in this project can be further engineered to delicately control nanoscale energy density, electromagnetic wave propagation, and photonic density of states for practical applications in biosensing, energy transfer, infrared light sources, and quantum information and technologies.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.