Effect of helical edge states on the tunneling conductance in ferromagnet/noncentrosymmetric superconductor junction
Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, 700032 Kolkata, India
2 Asia Pacific Center for Theoretical Physics, Hogil Kim Memorial building 5th floor, POSTECH, Hyoja-dong, Namgu, 790-784 Pohang, Korea
Corresponding author: a firstname.lastname@example.org
Revised: 1 February 2011
Published online: 1 March 2011
Helical edge states exist in the mixed spin-singlet and spin-triplet phase of a noncentrosymmetric (NCS) superconductor [Y. Tanaka, T. Yokoyama, A.V. Balatsky, N. Nagaosa, Phys. Rev. B 79, 060505(R) (2009)]. In this article we have considered a planar ferromagnetic metal/NCS superconductor tunnel junction and have studied the effect of these helical edge states which manifests itself through the charge and spin tunneling conductance across the junction. We have shown the behavior of conductance for the entire range of variation of γ = Δ-/Δ+ where Δ± are the order parameters in the positive and negative helicity bands of the NCS superconductor. There exists a competition between the Rashba parameter α and the exchange energy Eex which is crucial for determining the variation of the conductance with the applied bias voltage across the junction. We have found a nonzero spin current across the junction which appears due to the exchange energy in the Ferromagnet and modulates with the bias voltage. It also changes its profile when the strength of the exchange energy is varied.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2011