Regensburg 2025 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 2: 2D Semiconductors and van der Waals Heterostructures I
HL 2.1: Talk
Monday, March 17, 2025, 09:30–09:45, H15
Probing strong electron-phonon coupling in graphene by resonance Raman spectroscopy with infrared excitation energy — •Simone Sotgiu1,2, Tommaso Venanzi1, Lorenzo Graziotto1, Francesco Macheda1, Taoufiq Ouaj2, Elena Stellino1, Bernd Beschoten2, Christoph Stampfer2, Francesco Mauri1, and Leonetta Baldassarre1 — 1Department of Physics, Sapienza University of Rome, Rome, Italy — 2JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, Aachen, Germany
Resonance Raman spectroscopy (RRS) has been a key asset to study the interplay between electronic and vibrational properties of graphene. We report on RRS measurements with an excitation photon energy down to 1.17 eV on mono (MLG) and bilayer (BLG) graphene, to study how low-energy carriers interact with lattice vibrations. Thanks to the excitation energy close to the Dirac point, we unveil in the MLG a giant increase of the intensity ratio between the double-resonant 2D and 2D* Raman peaks with respect to graphite [1]. In BLG, the low excitation energy hampers some of the resonant Raman processes giving rise to the 2D peak. Consequently, the sub-features composing the 2D mode are spectrally more separated with respect to visible excitations. We compare experimental measurements on BLG with ab initio theoretical calculations and we trace back such modifications on the joint effects of probing the electronic dispersion close to the band splitting and enhancement of electron-phonon matrix elements [2]. [1] T. Venanzi et al., Phys. Rev. Lett. 2023, 130, 256901 [2] L. Graziotto et al., Nano Lett. 2024, 24, 1867
Keywords: Graphene; Raman; Electron-Phonon coupling; Infrared excitation energy