  We propose a four-terminal device designed to manipulate by all electrical
means the spin of a magnetic adatom positioned at the edge of a quantum spin
Hall insulator. We show that an electrical gate, able to tune the interface
resistance between a quantum spin Hall insulator and the source and drain
electrodes, can switch the device between two regimes: one where the system
exhibits spin pumping and the other where the adatom remains in its ground
state. This demonstrates an all-electrical route to control single spins by
exploiting helical edge states of topological materials.
