Seminar of Physics of Wrocław University of Technology
PWr, bud. A1, sala 322
Magnetism in Moiré Superlattices
dr hab. inż. Paweł Potasz
Wydział Fizyki, Astronomii i Informatyki Stosowanej, Uniwersytet Mikołaja Kopernika w Toruniu
Moiré superlattices formed by transition metal dichalcogenide (TMD) heterostructures are quantum simulators with highly tunable parameters. The bandwidth of top most valence band depends on moiré twist angle, while band filling factor can be changed by varying gate voltage. Many-body interacting states of triangular lattice Hubbard model have been already observed in moire superlattices, like Mott insulator states at one hole per superlattice unit cell, generalized Wigner crystal states and stripe charge orders at partial fillings. We investigate the magnetic properties of partially filled moiré energy bands using a combination of exact diagonalization and mean-field methods. We start from a continuum model and focus on electron-electron interactions for partially filled topmost valence band. We create maximally localized Wannier functions using the projection technique and derive effective Hubbard-like model. We obtain the many-body spectrum at particular fractional fillings and compare it with the one obtained from the Hubbard model, and confront with current experiments. The magnetic properties of the ground state are determined and the role of the non-local Coulomb interaction terms is identified, for both insulating and metallic states. Analysis of itinerant ferromagnetism is presented.
