3-<i>X</i> Structural Model and Common Characteristics of Anomalous Thermal Transport: The Case of Two-Dimensional Boron Carbides

Abstract

Improving the reliability of electronic devices requires effective heat management, and the key is the relationship between the thermal transport and temperature. Inspired by synthesized T-carbon and H-boron, the 3-<i>X</i> structural models are proposed to unify the two-dimensional (2D) multitriangle materials. Employing structural searches, we identify the stability of the 3-<i>X</i> configuration in 2D boron carbides as 3-9 BC₃ monolayer, which, unexpectedly, exhibits a linear thermal conductivity versus temperature, not the traditional ∼1/<i>T</i> trend. We summarize the common characteristics and explore why this behavior is absent in 3-9 AlC₃ and graphene via investigating the optical modes. We show that the linear behavior is a direct consequence of the special oscillation modes by the 3-<i>X</i> model associated with the largest group velocity. We find that 2D materials with such behavior usually share a relatively low thermal conductivity. Our work paves the way to deeply understand the lattice thermal transport and to widen nanoelectronic applications.