Enhanced coupling between massive fermions and zone-boundary phonons probed by infrared resonance Raman in bilayer graphene

Reference:

Graziotto, L., Macheda, F., Venanzi, T., Sotgiu, S., Ouaj, T., Stellino, E., Fasolato, C., Postorino, P., Metzelaars, M., Kögerler, P. and Beschoten, B., 2023. Enhanced coupling between massive fermions and zone-boundary phonons probed by infrared resonance Raman in bilayer graphene. arXiv preprint arXiv:2310.04071.

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Abstract:

Few-layer graphene possesses low-energy carriers which behave as massive fermions, exhibiting intriguing properties in both transport and light scattering experiments. By lowering the excitation energy of resonance Raman spectroscopy down to 1.17 eV we target these massive quasiparticles in the low-energy split bands close to the K point. The low excitation energy suppresses some of the Raman processes which are resonant in the visible, and induces a clearer frequency-separation of the sub-structures of the resonant 2D peak. Studying the different intensities of the sub-structures and comparing experimental measurements with fully abinitio theoretical calculations, in the case of bilayer graphene we unveil an enhanced coupling between the massive fermions and the lattice vibrations at the K point, in analogy to what found for the massless fermions of monolayer graphene, and also suggesting that what governs the enhancement is the vicinity of the electron-hole pair momentum to K rather than how small the electron-hole pair energy is.

Authors:

Lorenzo Graziotto,∗,1,8 Francesco Macheda,1,2 Tommaso Venanzi,1 Simone Sotgiu,1 Taoufiq Ouaj,3 Elena Stellino,4 Claudia Fasolato,5 Paolo Postorino,1 Marvin Metzelaars,6 Paul Kögerler,6 Bernd Beschoten,3 Matteo Calandra,7 Michele Ortolani,1 Christoph Stampfer,3 Francesco Mauri,1,2 and Leonetta Baldassarre1

Organisation / Department Address:

1 Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy

2 Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, 16163 Genoa, Italy

3 JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany

4 Department of Physics and Geology, University of Perugia, Via Alessandro Pascoli, 06123 Perugia, Italy

5 Institute for Complex System, National Research Council (ISC-CNR), 00185 Rome, Italy

6 Institute of Inorganic Chemistry, RWTH Aachen University, 52074 Aachen, Germany

7 Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo, Italy

8 Current Address: Institute of Quantum Electronics, ETH Zürich, Auguste-Piccard-Hof 1, 8093 Zürich, Switzerland