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O: Fachverband Oberflächenphysik

O 87: Graphene: Electronic Structure

O 87.7: Vortrag

Donnerstag, 19. März 2015, 16:30–16:45, MA 041

Chiral Enhanced Phonon Spectroscopy of Graphene — •Fabian D. Natterer¹, Yue Zhao^1,2, Jonathan Wyrick¹, Wen-Ying Ruan³, Yang-Hao Chan⁴, Mei-Yin Chou^3,4, Nikolai B. Zhitenev¹, and Joseph A. Stroscio¹ — ¹Center for Nanoscale Science and Technology, NIST, Gaithersburg, USA — ²University of Maryland, College Park, USA — ³Georgia Institute of Technology, Atlanta, USA — ⁴Academia Sinica, Taipei, Taiwan

In graphene, many phenomena are driven by the interaction with phonons, such as the relaxation of hot carriers or the mediation of many-body interactions. The proper characterization of phonons can therefore shed important insights into graphene based devices. Such devices were characterized by inelastic electron tunneling spectroscopy (IETS) but weak signals and other spectral features obscured a clear distinction between phonons and miscellaneous excitations. In this talk, I show that we are able to map large parts of the graphene phonon density of states by using a back gated graphene device, where the charge carrier density can be varied in magnitude and sign. Our averaging technique combines individual IETS data, obtained over the entire charge carrier range, with the benefit of improving the signal for inelastic excitations. Surprisingly, we observe that the graphene phonon intensity is enhanced when the charge carrier type is switched, indicating that this amplification occurs whenever the inelastic transition allows a change in the graphene chirality. The chiral enhancement follows a linear trend with energy and reaches almost an order of magnitude for the highest mode.