Generic continuum model formalism for moir\'e superlattice systems

Abstract

The moir\'e superlattice system provides an excellent platform for exploring various novel quantum phenomena. To theoretically tackle the diverse correlated and topological states emerging from moir\'e superlattices, one usually adopts an effective low-energy continuum model based on which the electron-electron effects are further considered. However, the construction of an accurate continuum model remains a challenging task, particularly for complex moir\'e superlattices such as twisted transition metal dichalcogenides. In this work, we develop a formalism for constructing generic continuum models that are in principle applicable for arbitrary moir\'e superlattices and are extrapolatable to any twist angles. Our key insight is that the microscopic electronic properties are intrinsic properties of the system, which should remain invariant across all twist angles; the lattice relaxations act as external inputs that vary with twist angles and are coupled with the electrons, and the coupling coefficients are characterized by intrinsic parameters. This partition enables a universal description of the angle variation of the continuum model using a single set of model parameters. To extract the model parameters, we design a numerical workflow based on data from first principles density functional theory calculations. We apply this framework to twisted bilayer MoTe$_{2}$, and obtain a single set of model parameters that accurately reproduce first-principles results, including electronic band structures, charge density distributions and Chern numbers, at three different twist angles. Furthermore, the model extrapolates robustly to smaller twist angles. Our work not only provides a more precise understanding of the microscopic properties of moir\'e superlattices, but also lays a foundation for future theoretical studies of low-energy electronic properties in generic moir\'e superlattice systems.