Continuous Mott transition in semiconductor moiré superlattices

Area of Science:

• Condensed Matter Physics
• Quantum Materials
• Materials Science

Background:

• The metal-insulator transition (MIT) from a Landau Fermi liquid to a Mott insulator is a key quantum phase transition.
• Understanding the critical region of this transition is crucial for discovering exotic states like quantum spin liquids and unconventional superconductivity.
• Semiconductor moiré superlattices offer a tunable platform to simulate condensed matter models, like the Hubbard model.

Purpose of the Study:

• To investigate the continuous metal-insulator transition (MIT) in a tunable moiré superlattice system.
• To explore the quantum critical phenomena associated with the transition to a Mott insulating state.
• To characterize the electronic and magnetic properties near the transition point.

Main Methods:

• Electrical tuning of effective electronic interaction strength in MoTe₂/WSe₂ moiré superlattices.
• Measurement of electrical resistance to identify the metal-insulator transition.
• Analysis of resistance scaling, charge gap, quasiparticle effective mass, and magnetic susceptibility.
• Investigation of Pomeranchuk effect in the metallic phase.

Main Results:

• A continuous MIT was observed at one electron per unit cell by tuning interaction strength.
• Evidence for quantum criticality includes resistance scaling collapse, vanishing charge gap, and diverging effective mass.
• Smooth magnetic susceptibility evolution and absence of long-range magnetic order suggest abundant low-energy spinful excitations in the insulator.

Conclusions:

• The study demonstrates a continuous Mott transition in a two-dimensional semiconductor moiré system.
• The observed phenomena align with universal critical theory for continuous Mott transitions.
• These findings provide a controllable platform for studying quantum criticality and exotic states near Mott insulators.