Thermal conductivity of sliding bilayer h-BN and its manipulation with strain and layer confinement

Two-dimensional bilayer structures exhibit novel properties not existing in the monolayer ones like bilayer hexagonal boron nitride (h-BN) with exotic interfacial ferroelectrics originated by laterally sliding one layer over the other (K. Yasuda, et al. , Science , 2021, 372 , 1458; M. Vizner Stern, et al. , Science , 2021, 372 , 1462). This intriguing property provides the sliding bilayer h-BN with promising applications in slidetronics. However, the thermal transport behaviour in the sliding bilayer h-BN is still unclear. Here, we systematically investigate the influence of the lattice configurations on the thermal conductivity ( κ ) of sliding bilayer h-BN structures as well as its manipulation with strain and layer confinement via first-principles. Our results show that structures with boron head-to-head stacking (B-B) exhibit lower κ values than the ones with nitrogen on the top of boron stacking (B-N). The phonon spectra and weighted phase space indicate a softer layer-breathing mode (ZO′) mode and higher three-phonon scattering rate of B-B patterns, leading to a lower κ . The moderate out-of-plane compressive strain of −6% significantly decreases the κ of B-B structures by about 50% through enhanced anharmonic scattering, while the higher strain of −18% suppresses the anharmonic scattering and increases the κ instead. Finally, we study the stacking dependence of the κ in tri-layer and bulk structures. The AC′ structure with B-B stacking exhibits a lower κ value due to the softer optical phonon modes. The strain further decreases κ by modulating the anharmonic phonon scattering.