Observation of Anomalous Phonon Softening in Bilayer Graphene - Condensed Matter > Mesoscale and Nanoscale PhysicsReport as inadecuate




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Abstract: The interaction of electron-hole pairs with lattice vibrations exhibits awealth of intriguing physical phenomena. The Kohn anomaly is a renowned examplewhere electron-phonon coupling leads to non-analytic phonon dispersion atspecific momentum nesting the Fermi surface. Here we report evidence of anothertype of phonon anomaly discovered by low temperature Raman spectroscopy inbilayer graphene where the charge density is modulated by the electric fieldeffect. This anomaly, arising from charge-tunable modulations of particle-holepairs that are resonantly coupled to lattice vibrations, is predicted toexhibit a logarithmic divergence in the long-wavelength optical-phonon energy.In a non-uniform bilayer of graphene, the logarithmic divergence is abated bycharge density inhomogeneity leaving as a vestige an anomalous phononsoftening. The observed softening marks the first confirmation of the phononanomaly as a key signature of the resonant deformation-potentialelectron-phonon coupling. The high sensitivity of the phonon softening tocharge density non-uniformity creates significant venues to explore theinterplay between fundamental interactions and disorder in the atomic layers.



Author: Jun Yan, Erik A. Henriksen, Philip Kim, Aron Pinczuk

Source: https://arxiv.org/







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