Scalable quaternary topological insulator for low-power spintronics

Topological insulators (TIs) with spin-momentum-locked surface states exhibit high charge-to-spin (C2S) conversion efficiency. However, binary and ternary TIs are constrained by a narrow tunable composition window for their insulating bulk states, which limits spintronic performance due to interference from bulk conduction. This work reports the development of a high-quality quaternary TI, [Sb2Te3(5−t)/Bi2Se3(t)]4, fabricated via scalable magnetron sputtering. By tuning the Bi2Se3 layer thickness, the quaternary TI exhibits high resistivity and low carrier concentration, effectively suppressing bulk conduction across a broad tunable window. Over a wide Bi2Se3 thickness range (t = 0.2–1.5 nm, corresponding to 3%–23% Bi2Se3 content), a high spin Hall angle (θSH) of 0.4–0.99 is maintained. Furthermore, in heterostructures based on this quaternary TI, the critical magnetization switching current density drops to as low as 3.3 × 105 A/cm2, which is two orders of magnitude lower than that of heavy metal Pt. Owing to the large spin Hall angle, the quaternary TI also exhibits power consumption approximately 20 times lower than ternary TIs for t = 0.2–1.5 nm. These results confirm that scalable quaternary TIs enable low-power spintronic devices with enhanced efficiency and processing flexibility, paving the way for advanced spintronic applications.