Spin-imbalance induced buried topological edge currents in Mott and topological insulator heterostructures

Abstract We theoretically investigate the heterostructure between a ferrimagnetic Mott insulator (MI) and a time-reversal invariant topological band insulator (TI) on the two-dimensional Lieb lattice with periodic boundary conditions. Our Hartree–Fock and slave-rotor mean-field results incorporate long-range Coulomb interactions. We present charge and magnetic reconstructions at the two edges of the heterostructure and reveal how buried topological edge modes adapt to these heterostructure edge reconstructions. In particular, we demonstrate that the interface magnetic field induces a spin imbalance in the edge modes while preserving their topological character and metallic nature. We show that this imbalance leads to topologically protected buried spin and charge currents. The inherent spin–momentum locking ensures that left and right movers contribute to the current at the two buried interfaces in opposite directions. We show that the magnitude of the spin-imbalance induced charge and spin current can be tuned by adjusting the spin–orbit coupling of the bulk topological insulator relative to the correlation strength of the bulk MI. Thus, our results demonstrate a controlled conversion of a spin Hall effect into an analog of a charge Hall effect driven by band topology and interaction effects. These topologically protected charge and spin currents pave the way for advances in low-energy electronics and spintronic devices.