We published a paper entitled “Copper-doped sputtered BiSb topological insulators for field-free perpendicular magnetization switching via out-of-plane spin polarization” in [Physical Review Materials 10, 064201 (2026)]. Achieving high SOT efficiency together with deterministic field-free switching is a key challenge for perpendicular-magnetization SOT-MRAM. In this work, we propose an effective strategy to realize high-efficiency field-free switching with an ultralow critical current density by doping copper into the topological insulator Bi_0.9Sb_0.1 (BiSb). The cosputtered Cu-BiSb alloy film achieves a high damping-like SOT efficiency (ξ_y,DL = 0.53) and, in contrast to undoped BiSb, a significant field-like torque induced by spin currents with out-of-plane spin polarization (ξ_z,FL = 0.55). This unconventional out-of-plane spin polarization enables deterministic field-free switching of perpendicular magnetization with a critical current density as low as ~4 MA/cm² in Cu-BiSb/Pt/Co/Pt heterostructures. Our work provides critical support for the development of TI-based, high-performance and integrable SOT-MRAM devices. Congratulations to Haotian Duan and co-workers!