Relativistic Mott transition in twisted WSe₂ tetralayers

Area of Science:

• Condensed matter physics
• Quantum electrodynamics
• Materials science

Background:

• Graphene's low-energy excitations are two-dimensional massless Dirac fermions.
• Electron-electron interactions could induce a relativistic Mott transition, giving Dirac fermions mass.
• This transition has been unobserved in pristine graphene due to insufficient interaction strength.

Purpose of the Study:

• To realize strongly correlated artificial graphene.
• To observe the relativistic Mott transition in a tunable system.
• To study the behavior of Dirac fermions under strong interactions.

Main Methods:

• Fabrication of twisted WSe2 tetralayers to create artificial graphene.
• Magnetotransport measurements to probe electronic properties.
• Tuning interaction strength by varying the twist angle.

Main Results:

• The artificial graphene's band structure mimics low-energy graphene.
• Observed hallmarks of massless Dirac fermions, including a π Berry phase and anomalous Landau fan.
• Demonstrated a semimetal-to-insulator transition by tuning the twist angle, indicating a Mott insulating state.

Conclusions:

• Successfully realized strongly correlated artificial graphene.
• Observed the relativistic Mott transition in this system.
• Opened new avenues for studying strongly correlated Dirac fermions in condensed matter.