Exceptional Thermal Switching Performance in 2D MoS 2 Due to Hexagonal to Rhombohedral Phase Transition and Polarization Switch

ABSTRACT Active control of heat flow is crucial for managing thermal energy in sustainable technologies. However, current technologies are limited by the small switching ratio and narrow operating temperature range of thermal switching materials. Herein, we demonstrate that molybdenum disulfide (MoS 2 ) exhibits an excellent thermal switching performance across an ultra‐wide temperature range of 300–1573 K, based on a reversible transition between the non‐polarized hexagonal (2H) and electronically polarized rhombohedral (3R) phases. This phase transition is kinetically limited, and the presence of electric field lowers the transition barrier, dramatically reducing the temperature and pressure required to drive the phase transition. The application of the electric field results in a vertical flip from the out‐of‐plane alignment along the pressure direction in the 2H phase (“off” state) to an in‐plane polarization alignment along the electric field direction in the 3R phase (“on” state). This phase transition and polarized orientation switching, in conjunction with the significant anisotropic thermal transport properties of both phases, lead to a record‐high thermal switching ratio of 15.2 at 300 K and maintains 6.6 at 1573 K. Our findings provide a new avenue for exploring high‐performance thermal switch material triggered by phase transition and orientation changes in highly anisotropic materials.