Terahertz Landau level spectroscopy of Dirac fermions in millimeter-scale twisted bilayer graphene

• URL: http://arxiv.org/abs/2504.20156v1
• Date: Mon, 28 Apr 2025 18:02:11 GMT
• Title: Terahertz Landau level spectroscopy of Dirac fermions in millimeter-scale twisted bilayer graphene
• Authors: Benjamin F. Mead, Spenser Talkington, An-Hsi Chen, Debarghya Mallick, Zhaodong Chu, Xingyue Han, Seong-Jun Yang, Cheol-Joo Kim, Matthew Brahlek, Eugene J. Mele, Liang Wu,
• Abstract summary: We leverage advances in fabrication to create twisted bilayer graphene samples over 5 mm x 5 mm in size with a uniform twist angle.<n>These measurements directly probe charge excitations in inter-Landau level transitions and determine the Fermi velocity as a function of twist angle.
• Score: 3.7030292478954383
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Exotic electronic physics including correlated insulating states and fractional Chern insulators have been observed in twisted bilayer graphene in a magnetic field when the Fermi velocity vanishes, however a question remains as to the stability of these states which is controlled by the gap to the first excited state. Free-space terahertz magneto-optics can directly probe the gap to charge excitations which bounds the stability of electronic states, but this measurement has thus-far been inaccessible due to the micron size of twisted bilayer graphene samples, while the wavelength of terahertz light is up to a millimeter. Here we leverage advances in fabrication to create twisted bilayer graphene samples over 5 mm x 5 mm in size with a uniform twist angle and study the magnetic field dependence of the cyclotron resonance by a complex Faraday rotation experiment in p-doped large angle twisted bilayer graphene. These measurements directly probe charge excitations in inter-Landau level transitions and determine the Fermi velocity as a function of twist angle.

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