Superconducting spintronics with magnetic domain walls

The recent experimental demonstration of spin-polarized supercurrents offers a venue for establishment of a superconducting analog to conventional spintronics. Whereas domain-wall motion in purely magnetic structures is a well-studied topic, it is not clear how domain-wall dynamics may influence superconductivity and whether some functional property can be harnessed from such a scenario. Here, we demonstrate that domain walls in superconducting systems offer a unique way of controlling the quantum state of the superconductor. Considering both the diffusive and ballistic limits, we show that moving the domain wall to different locations in a Josephson junction will change the quantum ground state from being in a 0 state to a p state. Remarkably, we also show that domain-wall motion can be used to turn on and off superconductivity: the position of the domain wall determines the critical temperature T-c and thus whether the system is in a resistive state or not, causing even a quantum phase transition between the dissipationless and normal state at T = 0. In this way, one achieves dynamical control over the superconducting state within a single sample by utilizing magnetic domain wall motion which has interesting consequences in terms of a domain-wall-controlled superconducting magnetoresistance effect.