Tunneling Conductance and Spin Transport in Clean Ferromagnet-Ferromagnet-Superconductor Heterostructures

Abstract

We present a transfer matrix approach that combines the Blonder-Tinkham-Klapwijk (BTK) formalism and self-consistent solutions to the Bogolibuov-de Gennes (BdG) equations and use it to study the tunneling conductance and spin transport in ferromagnet ($\mathrm{F}$)-superconductor ($\mathrm{S}$) trilayers (${\mathrm{F}}_1{\mathrm{F}}_2\mathrm{S}$) as functions of bias voltage. The self-consistency ensures that the spin and charge conservation laws are properly satisfied. We consider forward and angularly averaged conductances over a broad range of the strength of the exchange fields and $\mathrm{F}$ thicknesses, as the relative in-plane magnetization angle, $\varphi$, between the two ferromagnets varies. The $\varphi$-dependence of the self-consistent conductance curves in the trilayers can differ substantially from that obtained via a non-self-consistent approach. The zero bias forward conductance peak exhibits, as $\varphi$ varies, resonance effects intricately associated with particular combinations of the geometrical and material parameters. We find, when the magnetizations are non-collinear, signatures of the anomalous Andreev reflections in the subgap regions of the angularly averaged conductances. When ${\mathrm{F}}_1$ is half-metallic, the angularly averaged subgap conductance chiefly arises from anomalous Andreev reflection. The in-plane components of the spin current are strongly bias dependent, while the out-of-plane spin current component is only weakly dependent upon voltage. The components of the spin current aligned with the local exchange field of one of the F layers are conserved in that layer and in the S region, while they oscillate in the other layer. We compute the spin transfer torques, in connection with the oscillatory behavior of spin currents, and verify that the spin continuity equation is strictly obeyed in our method.

19 pages including figures. To appear in Phys. Rev. B; Fig12 is revised

References in corpus (11)

• Spin Transfer Torques
• A spin triplet supercurrent through the half-metallic ferromagnet CrO2
• Evidence for Triplet Superconductivity in a Superconductor-Ferromagnet Spin Valve
• Superconducting triplet spin valve
• Odd Triplet Pairing in clean Superconductor/Ferromagnet heterostructures
• Observation of the Triplet Spin-Valve Effect in a Superconductor-Ferromagnet Heterostructure
• Induced Triplet Pairing in clean s-wave Superconductor/Ferromagnet layered structures
• Angular dependence of superconductivity in superconductor / spin valve heterostructures
• Proximity effects and triplet correlations in Ferromagnet/Ferromagnet/Superconductor nanostructures
• Tunneling conductance in Superconductor/Ferromagnet junctions: a self consistent approach
• Scattering theory of magnetic/superconducting junctions with spin active interfaces

Cited by in corpus (3)

• General framework for transport in spin-orbit-coupled superconducting heterostructures: Nonuniform spin-orbit coupling and spin-orbit-active interfaces
• Magnetoelectric Andreev effect due to proximity-induced non-unitary triplet superconductivity in helical metals
• Transport in Ferromagnet/Superconductor spin valves