Topological insulators are bulk insulators but with surface states which are particularly robust to disorder and crystalline imperfections, for time reversal symmetric systems. Additionally, the surface topological electronic states exhibit a peculiar spin texture as well as a so-called massless Dirac energy dispersion, which make them fascinating materials for fundamental research but also in view of spin-based technologies. Furthermore, when magnetically doped or in close contact with another magnetic material, the induced local breaking of time reversal symmetry leads to gapped surface states, and the formation of new edge states at the surface boundaries, carrying a single quantum channel. Magnetic topological insulators are currently investigated for their future use in resistance standardization (using the so-called quantum anomalous Hall effect), as well as for their use in future spintronic applications. A challenging problem is however to probe the intrinsic features of these nontrivial edge states,
By elaborating a generic model of three-dimensional magnetically doped topological insulators embedded into a multiterminal device with ferromagnetic contacts near the top surface, and using nonlocal transport formalism, we found that the resistance measurements could give direct access to the local spin features of the chiral edge modes. Indeed, our simulations evidence that local spin polarization at the hinges inverts its sign between the top and bottom surfaces. At the opposite edge, the topological state with inverted spin polarization propagates in the reverse direction. As a result, a large resistance switch between forward and backward propagating states takes place, driven by the matching between the spin polarized hinges and the ferromagnetic contacts.
This feature is general to the ferromagnetic, antiferromagnetic, and canted antiferromagnetic phases, and enables the design of spin-sensitive devices. Our theoretical prediction opens a way to confirm the formation of those topological edge states, an essential step before further controlling those states for a variety of applications.
