Persistent spin current in a quantum-dot ring with Rashba spin–orbit coupling

By means of the non-equilibrium Green's function technique, the persistent spin and charge currents in a quantum-dot ring are theoretically investigated. We find that by introducing local spin–orbit interaction on an individual quantum dot, a pure persistent spin current can be induced even in the absence of external magnetic flux and magnetic material. Compared with persistent spin current in the quantum ring, the magnitude and direction of the persistent spin current can be controlled experimentally by means of adjusting the energy levels of quantum dots. In addition, a certain spin component of the persistent current can be suppressed by introducing an external magnetic flux.