Tunable anisotropic crystal spin transport in two-dimensional altermagnetic transition metal oxychalcogenides†
Abstract
Enhanced and tunable direction-dependent spin transport is highly desirable for high-performance spintronics applications; yet achieving this remains a significant challenge. Altermagnets, governed by specific crystal symmetries, have emerged as promising candidates, offering novel opportunities to manipulate direction dependent crystal spin transport. Here, we theoretically and computationally explore how tunable anisotropic spin transport can be realized in two-dimensional (2D) altermagnetic transition metal oxychalcogenides TM2Ch2O (where TM = V, Cr, Ni, Nb, Mo, Ta, and W; Ch = S and Se), which exhibit intrinsic spin–valley coupling. Taking monolayer Nb2S2O as an example, we demonstrate that enhanced direction-dependent crystal spin transport can be achieved by breaking the crystal symmetry. Specifically, applying uniaxial strain to monolayer Nb2S2O induces a longitudinal conductivity σxx in the spin-up channel that significantly exceeds σyy, whereas σyy dominates in the spin-down channel. Moreover, the application of external electric fields, in bilayer Nb2S2O, effectively yields distinct anisotropic spin transport profiles in each spin channel, with orthogonal principal directions between the two spin channels, thus facilitating tunable direction-dependent spin transport. Our findings not only deepen the understanding of transport physics in 2D altermagnets but also pave the way for further fundamental research and potential applications in device technologies.