Exploiting Coherence in Nonlinear Spin-Superfluid Transport

We show how the interference between superfluid spin currents can endow spin circuits with coherent logic functionality. While the hydrodynamic aspects of the linear-response collective spin transport obviate interference features, we focus on the nonlinear regime, where the critical supercurrent is sensitive to the phase accumulated by the condensate in a loop geometry. We propose to control this phase by electrical gating that tunes the spin-condensate coherence length. The nonlinear aspects of the spin superfluidity thus naturally lend themselves to the construction of logic gates, uniquely exploiting the coherence of collective spin currents. Vice versa, this functionality can be used to reveal the fundamental properties of spin superfluids.