  The evolution of a Landau Fermi liquid into a nonmagnetic Mott insulator with
increasing electronic interactions is one of the most puzzling quantum phase
transitions in physics. The vicinity of the transition is believed to host
exotic states of matter such as quantum spin liquids, exciton condensates and
unconventional superconductivity. Semiconductor moir\'e materials realize a
highly controllable Hubbard model simulator on a triangular lattice, providing
a unique opportunity to drive a metal-insulator transition (MIT) via continuous
tuning of the electronic interactions. Here, by electrically tuning the
effective interaction strength in MoTe2/WSe2 moir\'e superlattices, we observe
a continuous MIT at a fixed filling of one electron per unit cell. The
existence of quantum criticality is supported by the scaling behavior of the
resistance, a continuously vanishing charge-gap as the critical point is
approached from the insulating side, and a diverging quasiparticle effective
mass from the metallic side. We also observe a smooth evolution of the
low-temperature magnetic susceptibility across the MIT and find no evidence of
long-range magnetic order down to ~ 5% of the Curie-Weiss temperature. The
results signal an abundance of low-energy spinful excitations on the insulating
side that is further corroborated by the presence of the Pomeranchuk effect on
the metallic side. Our results are consistent with the universal critical
theory of a continuous MIT from a Landau Fermi liquid to a nonmagnetic Mott
insulator in two dimensions.
