Tunable Thermal Transport in Hole-Doped Monolayer Penta-Graphene: A First-Principles and Machine Learning Study

In conventional semiconductors, electron\textendash phonon coupling (EPC) is weaker than phonon\textendash phonon (ph-ph) scattering and plays little role in lattice thermal conductivity ($\kappa_{L}$). We show, using first-principles calculations combined with machine-learning force fields (FMLP), that EPC can instead dominate phonon transport in monolayer penta-graphene under carrier doping. The absence of mirror symmetry allows direct coupling of flexural (ZA) phonons to carriers, and tuning the Fermi level into the Van Hove singularity (VHS) strongly enhances the electronic density of states (el-DOS) and amplifies EPC. Consequently, $\kappa_{L}$ is suppressed by nearly 64\% (from 266 to $\sim$96 W\,m$^{-1}$\,K$^{-1}$ at room temperature) and exhibits a weakened temperature dependence (from $T^{-1.4}$ to $T^{-1.0}$). This EPC-driven suppression of heat transport enhances the thermoelectric figure of merit by more than threefold. These findings open a pathway to engineer heat conduction in low-symmetry carbon allotropes via controlled doping.