Diverse Strain Dependent Thermal Transport in 2D Materials

Manipulation of thermal transport is in increasing demand as heat transfer plays a critical role in a wide range of practical applications. While 3D bulk materials usually exhibit decreased lattice thermal conductivity upon mechanical stretching and enhanced thermal transport by compression, the thermal response of 2D materials to mechanical strain is not that simple. Perfectly planar atomically-thin materials such as graphene have reduced thermal transport ability when stretched. In contrast, some 2D materials with intrinsic buckled structure will possess enhanced thermal conductivity upon tension. However, many exceptions exist in other 2D materials. The thermal conductivity of 2D planar group III-nitrides (h-BN, h-AlN, h-GaN) is tremendously enhanced by stretching. By deeply analyzing the orbital projected electronic structure, we establish a microscopic picture of the lone-pair electrons driving strong phonon anharmonicity in group III-nitrides. However, the lone-pair electrons do not necessarily lead to enhanced thermal conductivity in strained penta-like 2D materials. Our findings offer perspectives of modulating thermal transport properties of broad 2D materials for applications such as thermoelectrics, thermal circuits, and nanoelectronics.