Research Projects

Oxide materials exhibit remarkable diversity in their structure and properties and have been extensively investigated over several decades. While many aspects of oxides (for example, mobility, purity, controlled growth, imaging) have improved significantly in the last decade, their interfaces with other materials, critical to any of their applications are yet to be understood. In the last two decades, since the discover of topological insulators, a number of quantum materials (the ones whose electronic structure exhibit nontrivial quantum geometry) have been studied and shown to exhibit remarkable exotic states at the surfaces. A surface is a special case of an interface (it is an interface between a material and vacuum). Hence, interfaces are even more important in the context of quantum materials like topological insulators, Weyl semimetals and so on. Similarly, topological features (eg skyrmions, vortices) in ordered states in ferroics have been quite interesting of late, as they can be fundamentally interesting as well as important to technological applications. Interestingly, such defects or features too are sensitive to boundary conditions which are controlled by their interfaces with other materials or the rest of the world. In summary, interfaces of ferroics and topological systems provide tremendous opportunities for exciting science and innovative devices. One example of this is a proposal by the PI of a new class of spectroscopies based on quantum geometry, which was demonstrated in 2D materials. This is a new type of Raman-like effect, which can measure vibrational spectrum of a crystal using electric circuit or light. This means a new application of a quantum material in which it can be used as a sensitive substrate in studies of another material. There is tremendous scope in developing new directions of research in these areas. Topology enters in modern physics of materials at least in two manners: (a) topological phases that are characterized by the symmetry protected surface or edge states though the bulk-boundary correspondence, and (b) topological defects or features in the ordered phases (e.g. domain walls, skyrmions) which depend on boundary conditions. Both of which involve boundaries or boundary conditions. The work here will focus on (i) interfaces between various topological 2D and 3D materials, with emphasis on the effects of quantum geometry and lowering of symmetry at the interfaces, and (b) topological defects (particularly domain walls, faults) or textures of ordered states in antiferromagnetic and ferroelectric orders exhibited by 3D oxides and 2D materials. Such structures too are interfaces.