Energy-efficient field-free unconventional spin-orbit torque magnetization switching dynamics in van der Waals heterostructures

Van der Waals (vdW) heterostructure of two-dimensional (2D) quantum materials offers a promising platform for efficient control of magnetization dynamics for non-volatile spin-based devices. However, energy-efficient field-free spin-orbit torque (SOT) switching and spin dynamics experiments to understand the basic SOT phenomena in all-2D vdW heterostructures are so far lacking. Here, we demonstrate energy-efficient field-free spin-orbit torque (SOT) switching and tunable magnetization dynamics in a vdW heterostructure comprising out-of-plane magnet Fe3GaTe2 and topological Weyl semimetal TaIrTe4. We measured the non-linear second harmonic Hall signal in TaIrTe4 /Fe3GaTe2 devices to evaluate the SOT-induced magnetization dynamics, which is characterized by a large and tunable out-of-plane damping-like torque. Energy-efficient and deterministic field-free SOT magnetization switching is achieved at room temperature with a very low current density. First-principles calculations unveil the origin of the unconventional charge-spin conversion phenomena, considering the crystal symmetry and electronic structure of TaIrTe4. These results establish that all-vdW heterostructures provide a promising route to energy-efficient, field-free, and tunable SOT-based spintronic devices.