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Non-collinear Andreev reflections in semiconductor nanowires

We show that noncollinear Andreev reflections can be induced at interfaces of semiconductor nanowires with spin-orbit coupling, Zeeman splitting and proximity-induced superconductivity. In a noncollinear local Andreev reflection, the spin polarizations of the injected and the retro-reflected carriers are typically at an angle which is tunable via system parameters. While in a nonlocal transport, this noncollinearity enables us to identify and block, at different voltage configurations, the noncollinear cross Andreev reflection and the direct charge transfer processes. We demonstrate that the intriguing noncollinearity originates from the spin-dependent coupling between carriers in the lead and the lowest discrete states in the wire, which, for a topological superconducting nanowire, are related to the overlap-induced hybridization of Majorana edge states in a finite system. These interesting phenomena can be observed in semiconductor nanowires of experimentally relevant lengths, and are potentially useful for spintronics.