 In 2006 Das Sarma with Euyheon Hwang provided the basic theory for collective modes and dielectric response in graphene and related chiral two-dimensional materials.In 2011 Das Sarma and collaborators introduced a new class of lattice tight-binding flat-band systems with nontrivial Chern numbers which belongs to the universality class of continuum quantum Hall and fractional quantum Hall systems without any external magnetic fields.Such flat-band tight-binding systems with non-trivial Chern numbers have substantially enhanced the types of possible physical systems for the realization of topological matter.