📝 SummarXiv

Abstract

The coupling between real-space inhomogeneities coordinates and spin (r-s) provides an alternative route to achieve efficient spin manipulation in spintronics beyond the conventional momentum-spin (k-s) coupling paradigm. Here we demonstrate an unexpected manifestation of one-dimensional (1D) r-s coupling in two-dimensional (2D) altermagnetic second-order topological insulators, where the spin-split floating edge states -- energetically isolated within the bulk band gap -- emerge and exhibit both N\'eel-vector-dependent and electrically tunable behaviors. The 1D edge-spin $\boldsymbol{r}$-$\boldsymbol{s}$ coupling ensures carrier transport to be exclusively carried by the edge states with quantized spin conductance, giving rise to an unconventional edge tunnel magnetoresistance (edge-TMR) effect that can be switched On or Off. As a proof of concept, we computationally design an edge-TMR device based on Cr$_2$Se$_2$O monolayer to demonstrate its edge transportation and controllability via the N\'eel order or electric field. Our findings propose a general prototype altermagnetic device for next-generation low-dimensional spintronics.