Competing magnetic states in transition metal dichalcogenide moire materials

Small-twist-angle transition metal dichalcogenide (TMD) heterobilayers develop isolated flat moire bands that are approximately described by triangular lattice generalized Hubbard models [F. Wu, T. Lovorn, E. Tutuc, and A. H. MacDonald, Phys. Rev. Lett. 121, 026402 (2018)]. In this paper we explore the metallic and insulating states that appear under different control conditions at a density of one electron per moire period and the transitions between them. By combining fully self-consistent Hartree-Fock theory calculations with strong-coupling expansions around the atomic limit, we identify four different magnetic states and one nonmagnetic state near the model phase diagram's metal-insulator phase transition line. Ferromagnetic insulating states, stabilized by nonlocal direct exchange interactions, are surprisingly prominent.

Automated summary

This study focused on the isolated flat moire bands in small-twist-angle transition metal dichalcogenide (TMD) heterobilayers, which are approximately described by triangular lattice generalized Hubbard models. The research explored metallic and insulating states under different control conditions at a density of one electron per moire period, and identified four different magnetic states and one nonmagnetic state near the metal-insulator phase transition line on the model phase diagram. Surprisingly, ferromagnetic insulating states stabilized by nonlocal direct exchange interactions were found to be prominent.