The ability to tune the energy gap in bilayer graphene makes it the perfect playground for the study of the effects of internal electric fields, such as the crystalline field, which are developed when other layered materials are deposited on top of it. Here, we introduce a novel device architecture allowing simultaneous control over the applied displacement field and the crystalline alignment between two materials. Our experimental and numerical results confirm that the crystal field and electrostatic doping due to the interface reflect the 120° symmetry of the bilayer graphene/BN heterostructure and are highly affected by the commensurate state. These results provide unique insight into the role of twist angle in the development of internal crystal fields and intrinsic electrostatic doping in heterostructures. Our results highlight the importance of layer alignment, beyond the existence of a moiré superlattice, to understand the intrinsic properties of a heterostructure.

Flat bands in moiré systems are exciting new playgrounds for the generation and study of exotic many-body physics phenomena in low-dimensional materials. Such physics is attributed to the vanishing kinetic energy and strong spatial localization of the flat-band states. Here, we use numerical simulations to examine the electronic transport properties of such flat bands in magic-angle twisted bilayer graphene in the presence of disorder. We find that while a conventional downscaling of the mean free path with increasing disorder strength occurs at higher energies, in the flat bands the mean free path can actually increase with increasing disorder strength. This phenomenon is also captured by the disorder-dependent quantum metric, which is directly linked to the ground state localization. This disorder-induced delocalization suggests that weak disorder may have a strong impact on the exotic physics of magic-angle bilayer graphene and other related moiré systems.

L’UCLouvain a l’honneur d’accueillir Jean-Marie Lehn, prix Nobel de chimie en 1987, pour une conférence exceptionnelle. Ce grand scientifique, pionnier de la chimie supramoléculaire, échangera avec les chercheur·euses et étudiant·es sur l'impact de ses découvertes et les défis futurs de la discipline.

Morpholines are prevalent in medicinal chemistry due to their favorable pharmacokinetic properties and widespread presence in FDA-approved drugs. Existing methods for morpholine synthesis often require prefunctionalized or protected reagents, limiting their versatility and efficiency. Here, we present a photocatalytic, diastereoselective annulation strategy for the synthesis of morpholines directly from readily available starting materials. This method employs a visible-light-activated photocatalyst, Lewis acid, and Brønsted acid to achieve high yields and stereoselectivity. It also provides access to diverse substitution patterns, including challenging tri- and tetra-substituted morpholines. Mechanistic studies reveal that the reaction proceeds through the formation of a radical cation intermediate, with triflic acid playing critical roles in protonating the substrate, preserving the photocatalyst, and preventing product oxidation. Beyond morpholines, this strategy is extended to piperidines, pyrrolidines, and other privileged nitrogen heterocycles. Our findings provide a modular approach for constructing complex, medicinally valuable scaffolds, advancing both synthetic and medicinal chemistry.