Chemical Design and Assembly of 2D Molecular-Atomic Lattice vdW Heterostructures for Quantum Emission

Non-Technical Summary: Quantum materials can be used to address profound challenges in information technology, health, and sustainability. With support from the Solid State and Materials Chemistry program in NSF’s Division of Materials Research, Prof. Thomas Kempa and his group at Johns Hopkins University search for new quantum platforms and focus on using few-atom-thick molecular crystal lattices to manipulate the optical emission properties of two-dimensional (2D) semiconductor layers. An important and unique feature of the quantum materials platform is that the molecular crystal lattice can be chemically modified so that the optical properties of the 2D semiconductor can also be tuned. To build this platform, which could potentially function as a quantum light source, the researchers use chemical design strategies and synthesis of molecular crystal lattices called metal-organic frameworks. They then show how to merge them with 2D semiconductors to yield layered heterostructures. These heterostructures represent a large departure from conventional approaches and could provide a route towards unprecedented materials integration, interface design, and property discovery. These efforts contribute to future quantum technologies that enable more sustainable high-performance computing, more powerful biological and chemical sensors, and more secure communications, all of which serve US national interests. Aside from this, the principal investigator spearheads two outreach efforts intended to educate diverse communities on the practical and ethical impacts of quantum information science, and to educate undergraduate and graduate students how to be more effective communicators of quantitative information through visual media (e.g., slides, figures, simulations). Technical Summary: Quantum materials display a host of intriguing phenomena including superconductivity, giant magnetoresistance, spin liquid states, and single photon emission, to name a few. However, despite great progress, much work remains to develop quantum materials that can address profound and growing societal challenges in information technology, health, and sustainability. Prof. Thomas Kempa and his group at Johns Hopkins University present a new material platform on which to elicit and manipulate quantum emission through atomically-precise control of excitons. The material platform is comprised of two-dimensional (2D) metal-organic frameworks (MOFs) layered with 2D transition-metal dichalcogenides (TMDs) creating so-called van der Waals heterostructures. A key feature of the platform is that the 2D MOFs can be chemically tailored to provide periodic potentials with bespoke symmetries, sizes, and strengths. In turn, the interaction of these potentials with a 2D TMD, or other 2D material, can elicit new excitonic phenomena. The research addresses two core objectives focused on (a) chemical design of 2D MOFs with bespoke topology and charge order and (b) assembly of 2D MOFs and 2D TMDs into vdW heterostructures. The proposed vdW heterostructure platform likely represents the first attempt to alter explicitly the exciton landscape within a 2D TMD through a tailored 2D molecular lattice. It also differs markedly from twistronic approaches that elicit moiré potentials, because the strategy Prof. Thomas Kempa and his group use provides for independent, chemically selective control over the potential thereby offering a vast new parameter space for materials integration, interface design, and property discovery. Besides its many intellectual merits, the research has broader impacts by contributing improvements to the performance and sustainability of computing hardware, and by contributing to the education and greater engagement of society with science. The latter impact occurs through two specific outreach efforts: a biannual JHU–Morgan State University “Quantum Computing and Security Workshop” to broaden community awareness of quantum information science, and a freely available training module called “From Data to Impact” that teaches students how to create salient and impactful figures, tables, and graphics. 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.