Modulation of Surface‐Associated Transport in (Bi 1‐x Sb x ) 2 Te 3 Gabriel Vinicius de Oliveira Silva, Reza Asadi, He Ren, Rabiul Islam, Jagadeesh Moodera, Guo‐Xing Miao
ABSTRACT
Topological insulators (TIs) possess unique topological surface states (TSS) with strong spin‐momentum locking. This leads to a large net surface spin accumulation when a surface charge current flows, thereby efficiently exerting a strong spin‐orbit torque (SOT) on an adjacent ferromagnet. However, the effectiveness of TSS transport is largely constrained by the Fermi‐level (E F ) position set by composition during growth and can hardly be adjusted afterward. In this work, we investigate the effectiveness of solid‐state iontronic gating for modulating the relative contributions of bulk‐like and surface‐associated transport in (Bi 1‐x Sb x ) 2 Te 3 (BST) at technologically relevant gate biases (V g < 2 V). In a battery‐inspired device geometry, a 7 QL‐thick BST is interfaced with a solid‐state electrolyte and an anode‐like Li‐ion reservoir, thereby making the cathode‐like BST gate‐tunable. Using magnetotransport measurements together with phenomenological two‐carrier/weak anti‐localization (WAL) analyses, we track gate‐dependent transport signatures consistent with a valve‐like modulation of surface‐associated transport fingerprints, with the strongest WAL‐associated coherent transport signatures emerging near the transport‐defined carrier compensation regime. Our findings suggest that this battery‐like three‐terminal device geometry can be a promising strategy for low‐voltage reconfigurable spintronic applications such as tunable SOT, directional spin information processing, or quantum information channel allocation.