New Twists on Chemistry and Physics in Atomically Layered Materials

Atomically thin or two-dimensional (2D) materials can be assembled into bespoke heterostructures to produce some extraordinary physical phenomena. Likewise, these highly tunable materials are useful platforms for exploring fundamental questions of interfacial chemical/electrochemical reactivity. One exciting and relatively recent example is the formation of moiré superlattices from azimuthally misoriented (twisted) layers. These moiré superlattices result in flat bands that lead to an array of correlated electronic phases. This talk will discuss how the localized electronic states in moiré superlattices also establish these materials as distinctive platforms for studying and controlling interfacial electrochemical reactions. In addition, in these systems, complex strain relaxation can also strongly influence the electronic states of the material. Precise characterization of these materials and their properties is therefore critical to the understanding of the physical and chemical behavior of these novel moiré materials (and 2D heterostructures in general). The talk will show how spontaneous mechanical deformations (atomic reconstruction) and resultant intralayer strain fields at moiré superlattices of twisted graphene sheets and transition metal dichalcogenides have been quantitatively imaged using 4D-STEM Bragg interferometry and the impact of these mechanical deformations on the electronic band structure (with ramifications for both the physics and chemistry of these materials). Finally, the talk will describe new approaches for synthesizing two-dimensional magnetic materials using chemical intercalation and the prospects for these materials as components of ultralow-power electronic devices.