Abstract

Identifying the microscopic processes that limit conductivity is essential for understanding correlated and quantum-critical states in quantum materials. In twisted bilayer graphene (TBG) and other twist-controlled materials, the temperature dependence of metallic resistivity follows ρ ∼ T^α scaling with competing interpretations. Here, terahertz excitation selectively raises the electron temperature in TBG while keeping the lattice cold, enabling separation of electron–electron and electron–phonon contributions to resistivity. The authors observe a giant THz photoresistance reaching up to 70%, demonstrating that electronic interactions dominate transport even near the magic angle. Away from the magic angle, photoresistance coexists with robust quadratic-in-T resistivity at extremely low carrier densities where standard electron–electron scattering mechanisms are kinematically forbidden. The analysis points to breakdown of Galilean invariance in Dirac-type dispersion as a possible origin of interaction-limited conductivity via intervalley electron–electron collisions.

Abstract

Identifying the microscopic processes that limit conductivity is essential for understanding correlated and quantum-critical states in quantum materials. In twisted bilayer graphene (TBG) and other twist-controlled materials, the temperature dependence of metallic resistivity follows ρ ∼ T^α scaling with competing interpretations. Here, terahertz excitation selectively raises the electron temperature in TBG while keeping the lattice cold, enabling separation of electron–electron and electron–phonon contributions to resistivity. The authors observe a giant THz photoresistance reaching up to 70%, demonstrating that electronic interactions dominate transport even near the magic angle. Away from the magic angle, photoresistance coexists with robust quadratic-in-T resistivity at extremely low carrier densities where standard electron–electron scattering mechanisms are kinematically forbidden. The analysis points to breakdown of Galilean invariance in Dirac-type dispersion as a possible origin of interaction-limited conductivity via intervalley electron–electron collisions.

Abstract

Identifying the microscopic processes that limit conductivity is essential for understanding correlated and quantum-critical states in quantum materials. In twisted bilayer graphene (TBG) and other twist-controlled materials, the temperature dependence of metallic resistivity follows ρ ∼ T^α scaling with competing interpretations. Here, terahertz excitation selectively raises the electron temperature in TBG while keeping the lattice cold, enabling separation of electron–electron and electron–phonon contributions to resistivity. The authors observe a giant THz photoresistance reaching up to 70%, demonstrating that electronic interactions dominate transport even near the magic angle. Away from the magic angle, photoresistance coexists with robust quadratic-in-T resistivity at extremely low carrier densities where standard electron–electron scattering mechanisms are kinematically forbidden. The analysis points to breakdown of Galilean invariance in Dirac-type dispersion as a possible origin of interaction-limited conductivity via intervalley electron–electron collisions.

Abstract

Identifying the microscopic processes that limit conductivity is essential for understanding correlated and quantum-critical states in quantum materials. In twisted bilayer graphene (TBG) and other twist-controlled materials, the temperature dependence of metallic resistivity follows ρ ∼ T^α scaling with competing interpretations. Here, terahertz excitation selectively raises the electron temperature in TBG while keeping the lattice cold, enabling separation of electron–electron and electron–phonon contributions to resistivity. The authors observe a giant THz photoresistance reaching up to 70%, demonstrating that electronic interactions dominate transport even near the magic angle. Away from the magic angle, photoresistance coexists with robust quadratic-in-T resistivity at extremely low carrier densities where standard electron–electron scattering mechanisms are kinematically forbidden. The analysis points to breakdown of Galilean invariance in Dirac-type dispersion as a possible origin of interaction-limited conductivity via intervalley electron–electron collisions.