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 spinincoherent 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.