Imaging and manipulating inter-particle interactions in van der Waals materials

Non-technical summary

Electronic and photonic technologies, from modern lasers to computers and solar cells, rely on the efficient transport and conversion of energetic particles such as electrons, excitons (neutral pairs of negative and positive charges), phonons (heat carriers), and photons (light). In almost all materials, these energetic particles co-exist and interact with one another. Unintentional inter-particle interactions are highly detrimental to modern device operation: for example, electron–phonon interactions are the primary efficiency loss mechanism in computer chips and solar panels. Nevertheless, if these interactions can be tailored and beneficially exploited, they can unlock massive efficiency improvements and new functionality in next-generation electronic, photonic and information technologies. In this project, the PI and his group are developing a new ultra-sensitive optical microscope to directly image and manipulate inter-particle interactions in a wide range of materials. The research focuses on two-dimensional semiconductors wherein particle interactions are dramatically enhanced. The goal of the project is to image electron–exciton and exciton–phonon interactions in emerging electronic materials, and to manipulate these interactions using light. This research should lead to new approaches for realizing multi-functional electronic and photonic platforms that can be rapidly reconfigured and that boast extraordinary energy transport properties. Broader goals include facilitating wide adoption of the team's new imaging approach by academic and industrial laboratories interested in developing materials with tailored energy transport properties by publishing extensive instrument blueprints, as well as posting an outreach video displaying a graduate student performing a full experimental cycle on the microscope to demystify the scientific process on state-of-the-art instrumentation.

Technical summary

Many-body interactions between electrons, excitons and phonons in semiconductors can suppress or enhance energy transport by orders of magnitude, and trigger exotic phases like superconductivity. These effects can be particularly strong in low-dimensional van der Waals semiconductors, where reduced volumes, quantum confinement and dielectric confinement all promote strong inter-particle interactions. Although they are known to play a crucial functional role, these interactions occur on extremely short time- and length-scales, making them notoriously difficult to study. The PI and his group are developing ultrasensitive, ultrafast optical scattering microscopes that uniquely track multiple photoexcited energetic particles and their interactions in real space on nanometer scales. This project involves the generalization of ultrasensitive scattering microscopy to reach single-particle sensitivity in a variety of materials over a broad range of temperatures. Using this unique tool, the research team focuses on imaging and manipulating electron–exciton interactions in transition metal dichalcogenides semiconductors and exciton–phonon interactions in superatomic assemblies. In both cases, the project seeks to create multi-functional material platforms that can be reconfigured by perturbing inter-particle interactions through fine-tuning of thermal and dielectric environments, or using external stimuli such as ultrafast light pulses. Through a much-refined understanding of many-body interactions in van der Waals materials, the team seeks to establish new forms of active control over long-range energy transport and conversion in classes of materials that will be key building blocks of next-generation electronic, photonic and information 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.