Softened sp2−sp3 bonding network leads to strong anharmonicity and weak hydrodynamics in graphene+

Abstract

Graphene+, a novel carbon monolayer with $s{p}^{2}\text{\ensuremath{-}}s{p}^{3}$ hybridization, was recently reported to exhibit unprecedented out-of-plane half-auxetic behavior and graphenelike Dirac properties [Yu et al., Cell Rep. Phys. Sci. 3, 100790 (2022)]. Herein, based on comprehensive state-of-the-art first-principles calculations, we reveal the significant effect of softened $s{p}^{2}\text{\ensuremath{-}}s{p}^{3}$ bonding on the lattice thermal transport in graphene+. At room temperature, the thermal conductivity (\ensuremath{\kappa}) of graphene+ is obtained as \ensuremath{\sim}170 W/mK, which is much lower than that of graphene (\ensuremath{\sim}3170 W/mK). It is found that the softened $s{p}^{2}\text{\ensuremath{-}}s{p}^{3}$ bonding significantly suppresses the vibrations of acoustic phonons in graphene+, which leads to strong anharmonicity and weak phonon hydrodynamics. Thus, the large reduction in \ensuremath{\kappa} stems from the softened $s{p}^{2}\text{\ensuremath{-}}s{p}^{3}$ bonding network. Our study provides fundamental physical insights into the thermal transport properties of graphene+, which would provide prospective guidance for the promising application in the field of thermal management.