Probing out of Equilibrium Electron-Phonon Behavior in Bilayer Graphene

Bilayer graphene exhibits unique electronic and optoelectronic properties, including a tunable bandgap and stacking-dependent electronic structure, that make it an ideal platform for exploring fundamental condensed matter phenomena. Thermal studies, in particular, provide a powerful means to probe the underlying electron–phonon interactions and vibrational dynamics that govern its behavior. In this work, we investigated the Raman response of bilayer graphene on a Si/SiO₂ substrate over a temperature range from 25 °C to 65 °C. We observed a systematic suppression of the G and 2D peaks and a broadening of the 2D peak with increasing temperature. These modifications arise from phonon anharmonicity, electron–phonon coupling, and temperature-dependent phonon lifetimes. Complementary density functional theory (DFT) calculations corroborate the experimental findings and reveal the microscopic origins of the observed changes. Our results demonstrate how temperature-dependent Raman spectroscopy provides insights into the fundamental physics of bilayer graphene, which can ultimately inform the rational design of future graphene-based devices.

Keywords: Bilayer graphene; Raman Spectra; Density Functional Theory.