Nonzero Berry curvature dipole, magnetic gapped edge states and persistent spin texture in a rotational symmetry preserved van der Waals magnetic topological insulator†

Abstract

Berry curvature dipole and persistent spin textures are unconventional quantum marvels with paramount relevance towards nonlinear transport phenomena and futuristic spintronic applications. Here, we demonstrate that a magnetic van der Waals (vdW) heterobilayer, comprised of semiconducting monolayers 1H-MoSe₂ (nonmagnetic) and ferromagnet 1H-VSe₂, exhibits a finite Berry curvature dipole (D_Bcd) in the absence of strain or twist perturbation, where each constituent layer displays no D_Bcd owing to three-fold (C_3v) rotational symmetry. A change in sign of D_Bcd is observed over an energy range, suggesting its oscillatory nature. Further, persistent spin texture (PST) with small spin canting and a prominent magnetic gap of 190 meV have emerged in the edge state spectrum of the vdW system. We find the emerged topological properties are crystal facet dependent. Moreover, an exotic quantum state of intrinsic spin–valley locking at two inequivalent K valleys with distinct spin identity is observed in the dispersion relation. We explore the subtle role of spin–valley locking in the generation of a finite D_Bcd, which has not been previously discussed in this context. Such quantum states promote right and left handed circular polarization and are perceived as a binary catalogue for information encoding and energy. Further, the role of symmetry breaking in the observed phenomena of the AB-stacked vdW heterobilayer is discussed. We propose that both time reversal symmetry breaking and spin–valley locking are essential for inducing nonzero D_Bcd in an AB stacked vdW heterostructure, where the three-fold (C₃) rotational symmetry is preserved along the z-axis only.