Tunable Infrared Phonon Anomalies in Trilayer Graphene

Abstract

Trilayer graphene in both ABA (Bernal) and ABC (rhombohedral) stacking sequences is shown to exhibit intense infrared absorption from in-plane optical phonons. The feature, lying at ~1580 cm-1, changes strongly with electrostatic gating. For ABC-stacked graphene trilayers, we observed a large enhancement in phonon absorption amplitude, as well as softening of the phonon mode, as the Fermi level is tuned away from charge neutrality. A similar, but substantially weaker effect is seen in samples with the more common ABA stacking order. The strong infrared response of the optical phonons and the pronounced variation with electrostatic gating and stacking-order reflect the interactions of the phonons and electronic excitations in the two systems. The key experimental findings can be reproduced within a simplified charged-phonon model that considers the influence of charging through Pauli blocking of the electronic transitions.

11 pages, 5 figures, supplemental material included

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Cited by in corpus (7)

• Stacking-dependent electronic structure of trilayer graphene resolved by nanospot angle-resolved photoemission spectroscopy
• Stacking-dependent shear modes in trilayer graphene
• Direct Probing Stacking Order and Electronic Spectrum of Rhombohedral Trilayer Graphene with Scanning Tunneling Microscopy
• First-principles theory of infrared vibrational spectroscopy in metals and semimetals: application to graphite
• Fano Resonances in the Infrared Spectra of Phonons in Hyper-Kagome Na_3Ir_3O_8
• Quick Identification of ABC Trilayer Graphene at Nanoscale Resolution via a Near-field Optical Route
• Electronic Structures and Their Landau Quantizations in Twisted Graphene Bilayer and Trilayer