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

Abstract

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

Ultrahigh Electron Thermal Conductivity in T‐Graphene, Biphenylene, and Net‐Graphene

“…There is an established notion that thermal energy transport in 2D carbon materials is largely phonon-based [32] and that the negligible electron-based conduction can become important only under n-doping. [33,34] Contrary to this notion, here we find that in 2D carbon allotropes with nonhexagonal rings, the electron thermal conductivity (κ e ), as calculated by considering electron-phonon (el-ph) scatterings, is of central importance. The large κ e compensates the drop in κ ph which is calculated here by including not only the three-phonon (3ph) but also the four-phonon (4ph) and phonon-electron (pe) scatterings.…”

“…The available experimental data for graphene, which is also shown, exhibits a large spread which may originate in both the sample variability (in terms of various defects and grain boundaries) [25] Faugeras et al, [37] Chen et al, [38] Lee et al, [39] Chen et al, [40] Li et al, [41] and Xie et al [42] ) and supported (Seol et al [51] ) graphene with different experimental sample size as well as the previous theoretical predictions of graphene (Lindsay et al [45] and Fugallo et al [46] ) are provided for comparison. c) Thermal conductivity of single-layer 2D materials at T = 300 K. Literature data (theoretical) for graphene, [35,45] h-BN, [52] 2D WS 2 and MoS 2 , [53] 2D MoSe 2 , [53] 2D BeN 4 , [34] silicene, [54] phosphorene, [55] SnSe, [56] and 2D MoO 3 . [36] The label on top of the bars denotes 3ph only, 3+4ph, and 3+4ph+pe scattering events for computing κ ph .…”

“…The latter contribution is neglected by other approaches, [28,29] but recently it was shown to cause strong suppression of κ ph in graphene, [35] MoO 3 , [36] and BeN 4 . [34]…”

“…[ 46 ] ) are provided for comparison. c) Thermal conductivity of single‐layer 2D materials at T = 300 K. Literature data (theoretical) for graphene, [ 35,45 ] h ‐BN, [ 52 ] 2D WS 2 and MoS 2 , [ 53 ] 2D MoSe 2 , [ 53 ] 2D BeN 4 , [ 34 ] silicene, [ 54 ] phosphorene, [ 55 ] SnSe, [ 56 ] and 2D MoO 3 . [ 36 ] The label on top of the bars denotes 3ph only, 3+4ph, and 3+4ph+pe scattering events for computing κ ph .…”

Thermal Properties of 2D Dirac Materials MN4 (M = Be and Mg): A First-Principles Study

“…The corresponding elastic moduli were 946(590) and 582(353) GPa, indicating high lattice thermal conductivities of BeN 4 monolayer, which has been proven also in other work. 20 In practice, some materials with high lattice thermal conductivities are useful for enhancing the heat dissipation in miniaturized and high-power nanoelectronic devices, which plays a fundamental role in thermal management. Therefore, it is crucial to investigate the lattice thermal conductivity in BeN 4 and MgN 4 monolayers.…”