Field-free switching of perpendicular magnetization by two-dimensional PtTe₂/WTe₂ van der Waals heterostructures with high spin Hall conductivity

The key challenge of spin–orbit torque applications lies in exploring an excellent spin source capable of generating out-of-plane spins while exhibiting high spin Hall conductivity. Here we combine PtTe₂ for high spin conductivity and WTe₂ for low crystal symmetry to satisfy the above requirements. The PtTe₂/WTe₂ bilayers exhibit a high in-plane spin Hall conductivity σ_s,y ≈ 2.32 × 10⁵ × ħ/2e Ω^–1 m^–1 and out-of-plane spin Hall conductivity σ_s,z ≈ 0.25 × 10⁵ × ħ/2e Ω^–1 m^–1, where ħ is the reduced Planck’s constant and e is the value of the elementary charge. The out-of-plane spins in PtTe₂/WTe₂ bilayers enable the deterministic switching of perpendicular magnetization at room temperature without magnetic fields, and the power consumption is 67 times smaller than that of the Pt control case. The high out-of-plane spin Hall conductivity is attributed to the conversion from in-plane spin to out-of-plane spin, induced by the crystal asymmetry of WTe₂. Our work establishes a low-power perpendicular magnetization manipulation based on wafer-scale two-dimensional van der Waals heterostructures.