Ultralow Thermal Conductivity of Layered Bi2O2Se Induced by Twisting

Although the twisting strategy has provided great opportunities to tune the electronic and optical properties of materials, little research has been done on how twisting affects phonon properties. Using machine-learning-based interatomic potentials within DFT-level quality and the perturbation theory to the fourth-order anharmonicity, the phonon transport properties are studied and the phonon behaviors of layered material Bi2O2Se when twisting is applied. It is found that the phonons of Bi2O2Se exhibit hardening effects at finite temperature, and the intrinsic lattice thermal conductivity along the out-of-plane (in-plane) direction is reduced to 3.21 (3.42) W/mK from 3.69 (4.55) W/mK at 300 K by including the four-phonon scattering. When introducing the twisting between the layers, the out-of-plane thermal conductivity can be further reduced by 83% as compared to that of the twist-free configuration. Such huge reduction of the thermal conductivity arises from the nearly flat acoustic phonon branches and the enhanced third- and fourth-order phonon anharmonicity due to the strong coupling between the twisted layers. These findings unravel that twisting is an effective strategy for tuning phonon band structure and phonon-phonon interactions, leading to ultralow lattice thermal conductivity of materials.