Significant Increase of Electron Thermal Conductivity in Dirac Semimetal Beryllonitrene by Doping Beyond Van Hove Singularity

2D beryllium polynitrides or beryllonitrene is a newly synthesized layered material displaying anisotropic Dirac cones and van Hove singularity (VHS) located only ?0.5 eV above the Fermi level. Using Boltzmann transport equation with many-body effects first-principles calculations, it uncovered that has an in-plane room-temperature phonon thermal conductivity (?ph) of 78.6 98.8 W mK?1, electron (?e) 23.0 60.7 along directions. ?ph dominated by large heat capacity flexural acoustic (ZA) modes, which are susceptible to three-phonon four-phonon scatterings but rather immune scattering onto electrons. Filling till VHS gradually enhances phonon–electron coupling monotonically decreases up 55%. Instead, ?e displays unusual nonmonotonic variations increase in carrier density follows states at corresponding levels. The results shed light on electrical properties reveal modulation mechanism includes 60% upon filling until VHS.