2007/12/22 by Jun Yan, Erik Henriksen, Erik A. Henriksen +3 · 1 citation
Materials Science · Physics and Astronomy · #Graphene research and applications #Mechanical and Optical Resonators #Topological Materials and Phenomena #cond-mat.mes-hall
paper · pdf · doi:10.1103/physrevlett.101.136804
published as Phys. Rev. Lett. 101, 136804 (2008) · 4 figures
arxiv created 2007/12/22 · openalex publication_date 2008/09/25 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The interaction of electron-hole pairs with lattice vibrations exhibits a wealth of intriguing physical phenomena such as the renowned Kohn anomaly. Here we report the observation in bilayer graphene of an unusual phonon softening that provides the first experimental proof for another type of phonon anomaly. Similar to the Kohn anomaly, which is a logarithmic singularity in the phonon group velocity [W. Kohn, Phys. Rev. Lett. 2, 393 (1959)], the observed phonon anomaly exhibits a logarithmic singularity in the optical-phonon energy. Arising from a resonant electron-phonon coupling effect, the anomaly was also expected, albeit not observed, in monolayer graphene. We propose an explanation for why it is easier to observe in bilayer samples.