Unraveling the two-channel thermal transport in bilayer graphene with twist angle engineering and electron-phonon coupling

Twisted bilayer graphene (T-BLG) has emerged as a compelling platform for investigating novel physical phenomena through moir\'e superlattices. Its exceptional electrical, magnetic, optical, and topological characteristics make it particularly promising for thermal management and thermoelectric applications. In this work, we present a systematic first-principles study comparing the two-channel thermal transport mechanisms between AB-stacked bilayer graphene (AB-BLG) and T-BLG, with a focus on higher-order phonon transport and electron-phonon coupling effects. Our results reveal that high-order anharmonicity significantly suppresses thermal conductivity in both systems, with a more pronounced effect in AB-BLG (42.0% reduction) compared to T-BLG (34.6% reduction) at 300 K. The enhanced four-phonon scattering in AB-BLG manifests as more distinct higher-order polynomial characteristics in quadratic residuals, primarily due to elevated four-phonon scattering rates within the low-frequency region ($0\ensuremath{\sim}10\phantom{\rule{0.16em}{0ex}}\mathrm{THz}$). Notably, T-BLG exhibits distinctive wavelike phonon transport characteristics, contributing 6% to the total thermal conductivity at 300 K and approaching 10% at temperatures above 600 K, while such effects remain negligible in AB-BLG. Moreover, electron-phonon interactions (EPI) dramatically influence thermal transport, particularly in T-BLG, where $p$-type doping (3 \ifmmode\times\else\texttimes\fi{} ${10}^{15}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}2}$) induces an 81.9% reduction in thermal conductivity, far exceeding the 31.0% reduction observed in AB-BLG. We attribute the enhanced electron-phonon coupling in T-BLG to its unique electronic band structure, characterized by stronger intervalley scattering, higher density of states near the Fermi level, and structural intrinsic disorder. Moreover, the stronger EPI effect in T-BLG is attributed to a broader spatial distribution enabled by symmetry breaking, which activates more scattering channels despite weaker average coupling strength. EPI also significantly suppresses the phonon coherence in AB-BLG and T-BLG. When the carrier concentration is at the maximum value of the electron density of states, the wavelike thermal conductivity reaches its minimum, and the suppression effect of the electron-phonon coupling on phonon coherence is strongest. These insights elucidate the distinct thermal transport mechanisms in bilayer graphene systems and suggest potential strategies for thermal conductivity modulation through twist angle engineering.