Spin-valley coupling and spin-polarized transport in a two-dimensional altermagnetic Cr2WS4 monolayer

Altermagnetism, characterized by momentum-dependent spin-splitting without net magnetization, attracts considerable attention due to its unique symmetry-governed electronic structures and potential applications in spintronic devices. Here, based on first-principles calculations, we identify Cr2WS4 monolayer as a two-dimensional tetragonal altermagnetic (AM) semiconductor. It exhibits a pair of energy degenerate valleys at X and Y points around the valence band maximum with opposite spin polarizations. We demonstrate that the degeneracy of X/Y valleys can be removed by in-plane uniaxial strain. Furthermore, the direction- and doping-dependent spin transport has been explored. Remarkably, we find that electron doping can lead to nearly 100% spin polarized currents in Cr2WS4 monolayer. These findings highlight the potential of AM semiconductors for low-power spintronic and spin-logic applications.