Title: Interfacial Dynamics and Structure: When do they matter for material function?
Abstract: It has alternatively been said that “The interface is the device” (Herbert Kroemer, 2000 Nobel Lecture) and that “God made the bulk; the surface was invented by the devil” (Wolfgang Pauli). This duality of interfaces, their critical importance but also the challenges associated with investigating interfacial properties, is what makes them a focus of research in my group. I will discuss different experimental approaches we use to probe the nanoscale structure and ultrafast dynamics of both internal and external interfaces in materials and discuss two examples. I will discuss an example where the structure of the interface impacts the domain structure of ferroelectric and antiferroelectric domains In2Se3. I will contrast this with an example from two-dimensional black phosphorus where the presence of an interface is not as important as the bulk material anisotropy. In these systems there is an interplay between the width of an interface compared with the relevant correlation length of excited and non-equilibrium states that plays a critical role in when an interface is deterministic for system and material function.