CRC 1772/1: Heterostructures of Molecules and 2D- Materials

The Collaborative Research Center (CRC) 1772 will study and exploit hitherto inaccessible collective phenomena and ground states of heterostructures composed of organic and inorganic molecules encapsulated by two-dimensional (2D) materials. Such heterostructures merge key features of 2D materials–crystalline order and delocalized excitations–with tunability via chemical synthesis, bright light emission, and chemical reactivity inherent to molecules. The focus of CRC1772 is emergent states caused by the coupling between the components of molecule/2D material (mol2Dmat) heterostructures. For example, excitations in individual molecules synchronize through molecule-molecule interactions and couple to waveguided photons within 2D materials. As a result, a collective light-matter state emerges. In a different example, charge-transfer excitons, electron-hole pairs delocalized between molecules and 2D materials, appear in mol2Dmat heterostructures. The energy of charge-transfer excitons is controlled by chemical synthesis or exposure to an external electric field. When their energy reaches zero, charge-transfer excitons condense into a macroscopic quantum state called an excitonic insulator. We will study such states by probes from electronic to optical, on time scales from femtoseconds to static, on length scales atomic to from hundreds of micrometers, and with theoretical tools from model-based Hamiltonians to numerical simulations. The proposed emergent states can only be realized by establishing molecular control over mol2Dmat heterostructures. Tailor-made donor, acceptor, dye, and photoswitchable molecules will be attached to one or both faces of 2D materials, all while controlling their orientation and the separation from the 2D basal plane. We will develop a conceptual understanding of processes relevant to mol2Dmat heterostructures, including charge transfer between their components and modification of chemical reactions. We will predict and verify the structure of mol2Dmat heterostructures. Our long-term vision is to develop device concepts leveraging emergent states, to realize novel phases of matter, and to trigger new reaction pathways in a confined two-dimensional space. Our proposed research center aligns perfectly with the CRC funding scheme through its cross-disciplinary spirit and future-focused orientation. It builds on the long-term focus of Freie Universit?t Berlin (FUB) in molecular, surface, and nanoscale science. Together with our three partner institutions, we will further connect physics and chemistry and promote early-career scientists in an emerging interdisciplinary field.