Nature of the bandwidth-tuned Mott transition in moire semiconductors
In plain words
In MoTe2/WSe2 and in twisted WSe2, 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.
Precise statement
In MoTe2/WSe2 heterobilayers (Li et al., Nature, 2021, arXiv:2103.09779) and twisted bilayer WSe2 (Ghiotto et al., Nature, 2021) at filling $\nu = 1$ (one hole per moire site of a triangular lattice), tuning the displacement field drives a metal-insulator transition at which the charge gap closes continuously and $\rho(T)$ shows quantum-critical scaling. Determine whether this is a continuous Mott transition from a Fermi liquid to a spin liquid with a spinon Fermi surface, a transition into a magnetically ordered insulator, or a disorder-broadened first-order transition. An answer specifies the insulating state, the critical exponents, and the behaviour of the effective mass and spin susceptibility at the critical point.
What would settle it
Thermodynamic measurement of electronic specific heat or spin susceptibility across the transition, together with optical or tunnelling measurement of the charge gap, showing whether a gapless spin sector survives in the insulator.
Status in the literature
Unverified note
Both 2021 experiments reported continuous transitions; explanations based on spinon Fermi surfaces, magnetic order and disorder all remain in use as of 2026, to this survey's knowledge.