Semiconductor moire Hubbard and Kondo lattices

4 problems

• Nature of the bandwidth-tuned Mott transition in moire semiconductors

  Contested

  In $\mathrm{MoTe_2}$/$\mathrm{WSe_2}$ and in twisted $\mathrm{WSe_2}$, the insulator with one electron per moire site turns into a metal as an electric field widens the band, and the change looks continuous, which standard theory does not expect for this kind of transition.

• Kondo breakdown transition in a gate-tuned moire Kondo lattice

  Open

  In $\mathrm{MoTe_2}$/$\mathrm{WSe_2}$ one layer can hold fixed local magnetic moments while the other carries mobile electrons, and the two combine into a heavy-electron metal (a Kondo lattice); how this metal breaks apart when the coupling between layers is weakened is unknown.

• Spin liquid near the Mott transition in a moire triangular lattice

  Open

  Computer studies of electrons on a triangular lattice predict that just on the insulating side of the metal-insulator transition the spins may form a spin liquid (no magnetic order even at zero temperature), and moire semiconductors could test this.

• Quantum melting of generalized Wigner crystals in moire semiconductors

  Open

  At fractional fillings such as one electron per three moire sites, electrons in $\mathrm{WSe_2}$/$\mathrm{WS_2}$ order into crystals because of their repulsion (generalized Wigner crystals), and how these crystals turn into metals as the repulsion is weakened is unknown.