1:00 pm MCP 201
Band flattening and correlated physics in twisted bilayer Bravais networks
Toshikaze Kariyado (NIMS/Harvard)
We demonstrate band flattening in twisted bilayers of the five two-dimensional Bravais networks: oblique, rectangular, square, diamond, and hexagonal [1]. We first show that the interlayer coupling that governs low-energy physics is subjected to symmetry based constraints. The constraints enables us to predict and understand the real space potential profile in the effective model under the influence of the moire pattern. Knowing the potential profile makes it easy to pin down the condition for trapping electrons to form flat bands. The power of the symmetry based constraints in predicting flat bands is numerically demonstrated using simple tight-binding models. From the generic theory, we further find an interesting possibility of anisotropic band flattening, in which quasi one-dimensional band dispersion is generated from relatively isotropic original band dispersion. Rich physics is expected in the strongly correlated regime for the anisotropic band flattening as a spin-orbital model with intertwined magnetic and orbital degrees of freedom.