The urgent demand of extreme (ultra-high/low) thermal conductivity materials is triggered by the high- power device, where exploring the theories and mecha- nisms of regulating thermal transport properties plays a key role. Herein, we elaborately investigate the effect of ver- tical (out-of-plane) piezoelectric characteristics on thermal transport, which is historically undiscovered. The different stacking-order (AA and AB) bilayer boron nitride (Bi-BN) in two-dimensional (2D) materials are selected as study cases. By performing state-of-the-art first-principles cal- culations, it is found that the polarization charge along the out-of-plane orientation ascends significantly with the increasing piezoelectric response in AB stacked Bi-BN (Bi-BN-AB) followed by the enhanced interlayer B–N atomic interactions. Consequently, the amplitude of pho- non anharmonicity in Bi-BN-AB increases larger than that in the AA stacked Bi-BN (Bi-BN-AA), resulting in the dramatic weakening of the thermal conductivity by 20.34% under 18% strain. Our research reveals the significant role of the vertical (out-of-plane) piezoelectric characteristic in regulating thermal transport and provides new insight into accurately exploring the thermal transport performance of 2D van der Waals materials.

This study was financially supported by the National Natural Science Foundation of China (Nos. 52006057, 51906097 and 11904324), the Fundamental Research Funds for the Central Universities (Nos. 531119200237 and 541109010001), and the State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body at Hunan University (No. 52175013). The numerical calculations have been done on the supercomputing system of the National Supercomputing Center in Changsha and the Lichtenberg high performance computer of the TU Darmstadt.