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Area of Science:

  • Condensed Matter Physics
  • Materials Science
  • Quantum Materials

Background:

  • Van Hove singularities are crucial for emergent phenomena like superconductivity and magnetism.
  • Magic-angle twisted bilayer graphene exhibits low-energy van Hove singularities sensitive to carrier density.
  • Linear transport measurements have limitations in probing band topology without magnetic fields.

Purpose of the Study:

  • To investigate the electronic band topology and Fermi surface reconstructions in twisted bilayer graphene at zero magnetic field.
  • To utilize nonlinear transport measurements as a sensitive probe of these phenomena.
  • To establish nonlinear transport as a key tool for understanding correlated electron systems.

Main Methods:

  • Nonlinear longitudinal and transverse transport measurements.
  • Analysis of responses induced by Berry curvature dipole and extrinsic scattering.
  • Probing twisted bilayer graphene at various carrier densities.

Main Results:

  • Nonlinear transport responses accurately map Fermi surface reconstructions.
  • The experiments reveal an intrinsic connection between observed features and moiré bands.
  • Findings corroborate and extend insights from linear Hall measurements.

Conclusions:

  • Nonlinear transport measurements are highly effective for probing band topology in twisted bilayer graphene.
  • This technique provides a powerful new avenue for studying correlated phenomena in moiré materials.
  • The study highlights the importance of Van Hove singularities in driving complex electronic states.