Rashba splitting of Cooper pairs

We investigate theoretically the properties of a weak link between two superconducting leads, which has the form of a non-superconducting nanowire with a strong Rashba spin-orbit coupling caused by an electric field. In the Coulomb blockade regime of single-electron tunneling, we find that such a weak link acts as a "spin splitter" of the spin states of Cooper pairs tunneling through the link, to an extent that depends on the direction of the electric field. We show that the Josephson current is sensitive to interference between the resulting two transmission channels, one where the spins of both members of a Cooper pair are preserved and one where they are both flipped. As a result, the current is a periodic function of the strength of the spin-orbit interaction and of the bending angle of the nanowire (when mechanically bent); an identical effect appears due to strain-induced spin-orbit coupling. In contrast, no spin-orbit induced interference effect can influence the current through a single weak link connecting two normal metals.Comment: 5 pages 3 figures. arXiv admin note: text overlap with arXiv:1306.512

Rashba proximity states in superconducting tunnel junctions

We consider a new kind of superconducting proximity effect created by the tunneling of "spin split" Cooper pairs between two conventional superconductors connected by a normal conductor containing a quantum dot. The difference compared to the usual superconducting proximity effect is that the spin states of the tunneling Cooper pairs are split into singlet and triplet components by the electron spin-orbit coupling, which is assumed to be active in the normal conductor only. We demonstrate that the supercurrent carried by the spin-split Cooper pairs can be manipulated both mechanically and electrically for strengths of the spin-orbit coupling that can realistically be achieved by electrostatic gates.Comment: Accepted for publication in Fiz. Niz. Temp./Low Temp. Phys. vol. 44, no. 6, 2018. arXiv admin note: text overlap with arXiv:1709.0802

Electric and Magnetic Gating of Rashba-Active Weak Links

In a one-dimensional weak-link wire the spin-orbit interaction (SOI) alone cannot generate a nonzero spin current. We show that a Zeeman field acting in the wire in conjunction with the Rashba SOI there does yield such a current, whose magnitude and direction depend on the direction of the field. When this field is not parallel to the effective field due to the SOI, both the charge and the spin currents oscillate with the length of the wire. Measuring the oscillating anisotropic magnetoresistance can thus yield information on the SOI strength. These features are tuned by applying a magnetic and/or an electric field, with possible applications to spintronics.Comment: 6 pages,4 figures, Supplemental materia

DC spin generation by junctions with AC driven spin-orbit interaction

An unbiased one-dimensional weak link between two terminals, subjected to the Rashba spin-orbit interaction caused by an AC electric field which rotates periodically in the plane perpendicular to the link, is shown to inject spin-polarized electrons into the terminals. The injected spin-polarization has a DC component along the link and a rotating transverse component in the perpendicular plane. In the adiabatic, low rotation-frequency regime, these polarization components are proportional to the frequency. The DC component of the polarization vanishes for a linearly-polarized electric field.Comment: published versio

Photo-spintronics of spin-orbit active electric weak links

We show that a carbon nanotube can serve as a functional electric weak link performing photo-spintronic transduction. A spin current, facilitated by strong spin-orbit interactions in the nanotube and not accompanied by a charge current, is induced in a device containing the nanotube weak link by circularly polarized microwaves. Nanomechanical tuning of the photo-spintronic transduction can be achieved due to the sensitivity of the spin-orbit interaction to geometrical deformations of the weak link.Comment: 4 pages, 3 figure