Abnormal enhancement of thermal conductivity by planar structure: A comparative study of graphene-like materials

Abstract

The traditional knowledge that the lone-pair electrons lead to low thermal conductivity provides important clues for the prediction of thermal conductivity and fundamental understanding on phonon transport. In this study, we reported a counterintuitive phenomenon that the thermal conductivity can increase by up to two orders of magnitude after activating the lone-pair electrons. Boron atoms are introduced to the two-dimensional (2D) nitrogene, blue phosphorene, arsenene, and antimonene to activate the lone-pair electrons, i.e., graphene-like boron nitride (g-BN), boron phosphide (g-BP), boron arsenide (g-BAs), and boron antimonide (g-BSb). This phenomenon is intuitively reflected in the competitive effect of phonon thermal transport (1) between in-plane and out-of-plane acoustic phonon modes, (2) between Grüneisen parameter and scattering phase space, and (3) between unbonded s-electrons pair and their space appearance. The essence of competition lies in the feedback adjustment of the structure to the electronic distribution, which reflects the high sensitivity of the thermal conductivity on the structure and overcomes the strong anharmonicity caused by the lone-pair electrons. Our study provides a counterexample to the traditional model of low thermal conductivity caused by lone-pair electrons. The results reported in this study provide a new perspective on the thermal transport, which is helpful to understand the key role of structure in phonon thermal transport in 2D materials.