Nonlinear intensity dependence of photogalvanics and photoconductance induced by terahertz laser radiation in twisted bilayer graphene close to magic angle

Abstract

We report on the observation of the nonlinear intensity dependence of the bulk photogalvanic current and photoconductivity in the twisted graphene with small twist angles close to the second magical angle. We show that terahertz radiation results in the photoresponses, which is caused by indirect optical transitions (free carrier absorption), direct interband transitions and optical transitions between Moiré subbands. The relative contribution of these absorption channels depends on the Fermi level position with respect to the multiple Moiré subbands of the twisted graphene. The interplay of these absorption channels results in oscillations of the photoresponses with variation of the gate voltage. We show that the photoresponse saturates at high intensities. For different absorption channels it has different intensity dependencies and saturation intensities. The latter depends non-monotonically on the Fermi level position, which is controlled by the gate voltage.

10 pages , 7 figures

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Cited by in corpus (7)

• Kondo Lattice Model of Magic-Angle Twisted-Bilayer Graphene: Hund's Rule, Local-Moment Fluctuations, and Low-Energy Effective Theory
• Symmetric Kondo Lattice States in Doped Strained Twisted Bilayer Graphene
• Dynamical correlations and order in magic-angle twisted bilayer graphene
• Infrared photoresistance as a sensitive probe of electronic transport in twisted bilayer graphene
• Nonlinear intensity dependence of ratchet currents induced by terahertz laser radiation in bilayer graphene with asymmetric periodic grating gates
• Intrinsic and extrinsic photogalvanic effects in twisted bilayer graphene
• Ferromagnetism vs. Antiferromagnetism in Narrow-Band Systems: Competition Between Quantum Geometry and Band Dispersion