Condensed Matter Journal Club: "From Carbon Atoms to Strongly Correlated Flat Bands"

Graphene provides a remarkable platform in which rich quantum phenomena emerge from simple microscopic ingredients. Starting from the electronic structure of monolayer graphene, I will discuss how its Dirac band structure, pseudospin winding, and valley-dependent topology arise from the underlying honeycomb lattice. Extending to multilayer graphene, different stacking configurations reshape the low-energy bands and can strongly suppress the electronic bandwidth. A similar mechanism appears in twisted bilayer graphene, where moiré interference near the magic angle produces nearly flat bands. 

These flat-band systems greatly enhance the role of electron-electron interactions and provide a natural setting for strongly correlated phases. I will conclude by discussing several experimental manifestations of this physics, including correlated insulating states, superconductivity, strange metallic behavior, and interaction-driven symmetry breaking and topological states.