Density functional approach to correlated moire states: itinerant magnetism

Two-dimensional moire superlattices have recently emerged as a fertile ground for creating novel electronic phases of matter with unprecedented control. Despite intensive efforts, theoretical investigation of correlated moire systems has been challenged by the large number of atoms in a superlattice unit cell and the inherent difficulty of treating electron correlation. The physics of correlated moire systems is governed by low-energy electrons in a coarse-grained long-wavelength potential, unlike the singular Coulomb potential of atomically-spaced ions in natural solids. Motivated by the separation between moire and atomic length scales, in this work we apply density functional theory to study directly the continuum model of interacting electrons in the periodic moire potential. Using this quantitatively accurate method, we predict itinerant spin-valley ferromagnetism in transition metal dichalchogenide heterobilayers, which originates from the constructive interplay between moire potential and Coulomb interaction in a two-dimensional electron system.