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تسجيل مستخدم جديدObservation of the Kohn anomaly near the K point of bilayer graphene
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The dispersion of electrons and phonons near the K point of bilayer graphene was investigated in a resonant Raman study using different laser excitation energies in the near infrared and visible range. The electronic structure was analyzed within the tight-binding approximation, and the Slonczewski-Weiss-McClure (SWM) parameters were obtained from the analysis of the dispersive behavior of the Raman features. A softening of the phonon branches was observed near the K point, and results evidence the Kohn anomaly and the importance of considering electron-phonon and electron-electron interactions to correctly describe the phonon dispersion in graphene systems.
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Kohn anomalies in three-dimensional metallic crystals are dips in the phonon dispersion that are caused by abrupt changes in the screening of the ion-cores by the surrounding electron-gas. These anomalies are also present at the high-symmetry points
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In neutral graphene, two prominent cusps known as Kohn anomalies are found in the phonon dispersion of the highest optical phonon at $q=Gamma$ (LO branch) and $q=K$ (TO branch), reflecting a significant electron-phonon coupling to undoped Dirac elect
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