Junctions of spin-incoherent Luttinger liquids with ferromagnets and superconductors

Abstract

We discuss the properties of a strongly interacting spin-charge separated one-dimensional system coupled to ferromagnets and/or superconductors. Our results are valid for arbitrary temperatures with respect to the spin energy, but require that temperature be small compared to the charge energy. We focus mainly on the spin-incoherent regime where temperature is large compared to the spin energy, but small compared to the charge energy. In the case of a ferromagnet we study spin pumping and the renormalized dynamics of a precessing magnetic order parameter. We find that the interaction-dependent temperature dependence of the spin pumping can be qualitatively different in the spin-incoherent regime from the Luttinger liquid regime, allowing an identification of the former. Likewise, the temperature dependence of the renormalized magnetization dynamics can be used to identify spin-incoherent physics. For the case of a spin-incoherent Luttinger liquid coupled to two superconductors, we compute the ac and dc Josephson currents for a wire geometry in the limit of tunnel coupled superconductors. Both the ac and dc responses contain “smoking gun” signatures that can be used to identify spin-incoherent behavior. Experimental requirements for the observation of these effects are laid out.

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