| Popis: |
This thesis studies several examples of how topology and interactions lead to novel electronic phenomena in magic-angle twisted bilayer graphene, a moire heterostructure that has attracted much attention owing its diversity of experimentally-observed correlated phases. Part I focuses on neutral and charged excitations of the correlated insulators predicted within the strong coupling framework, which emphasizes the close connections of the central moire bands to quantum Hall ferromagnetism. In Chapter 3, we show that topological excitons can be formed from the quantized anomalous Hall insulator at filling factor $\nu=+3$, and explore the possibility of a new excitonic fractional quantum Hall hierarchy. In Chapter 4, we study the properties of the three classes of domain walls that separate topological domains in this insulator. In Chapter 5, we use microscopic Hartree-Fock numerics to analyze charged spin and pseudospin skyrmions at various integer fillings, with an emphasis on the pairing of pseudospin skyrmions and its consequences for skyrmion superconductivity. Part II reconsiders the prevailing normal state phase diagrams of the strong coupling framework. In Chapter 6, we explore the effects of heterostrain, and demonstrate the emergence of a new electronic order, the incommensurate Kekule spiral, which possesses an unusual form of multiscale translation symmetry breaking. We argue that the phenomenology of the intermediate coupling regime is consistent with many experiments, and that strain and the incommensurate Kekule spiral are ingredients that should play important roles in any umbrella theory of twisted bilayer graphene. |
