Light-current conversion in single phase materials has been widely-studied. One of its main mechanisms is the bulk photovoltaic (BPV) effect. Other than electric charge current, generating pure spin current under light irradiation in a single material that only carries spin angular momentum without net electric currents is beneficial for high-performance spintronic devices. As both electric BPV and spin-resolved BPV require the breaking of inversion symmetry, they often emerge simultaneously. Hence, it is intriguing to design materials that could only host the spin BPV effect, while the electric charge current is completely suppressed, so that the Joule heating can be greatly eliminated. Furthermore, in order to increase spin lifetime and reduce spin decoherence, one promising route is the realization of a persistent spin helix in the momentum space. In this work, we scrutinize the point groups that could simultaneously host persistent spin helix in the momentum space and pure spin BPV generation, while the electric BPV process is symmetrically forbidden. We perform tight-binding model calculations and show that these requirements can be realized in a topological screw dislocation of centrosymmetric
crystal. We also evaluate orbital moment BPV generation that follows the same symmetry arguments with spin moment. As both spin and orbital angular momenta are not good quantum numbers, they would be subject to torque effects during transport. This has been largely overlooked in most previous works. Our calculations suggest that these angular momentum torques are significant and cannot be omitted. Moreover, we show that the topological gapless states and spin (orbital) BPV from the screw dislocation line defects can be manipulated through defect-defect interactions.
Link：Pure spin and orbital bulk photovoltaic effect in topological screw dislocations | Phys. Rev. B
