Chiral symmetry breaking and the Josephson current in a ballistic superconductor-quantum wire-superconductor junction

Artikel i vetenskaplig tidskrift, 2004

We evaluate the Josephson current through a quasi-1D quantum wire coupled to bulk superconductors. It is shown that the interplay of Rashba spin-orbit interaction and Zeeman splitting results in the appearance of a Josephson current even in the absence of any phase difference between the superconductors. In a transparent junction (Dsimilar or equal to1) at low temperatures this anomalous supercurrent J(an) appears abruptly for a Zeeman splitting of the order of the Andreev level spacing as the magnetic field is varied. In a low-transparency (Dmuch less than1) junction one has J(an)proportional torootD under special (resonance) conditions. In the absence of Zeeman splitting the anomalous supercurrent disappears. We have investigated the influence of dispersion asymmetry induced by the Rashba interaction in quasi-1D quantum wires on the critical Josephson current and have shown that the breakdown of chiral symmetry enhances the supercurrent.