Junctions of Spin-Incoherent Luttinger Liquids with Ferromagnets and Superconductors

TL;DR

This paper investigates the unique properties of spin-incoherent Luttinger liquids coupled to ferromagnets and superconductors, highlighting distinctive temperature-dependent behaviors that can serve as experimental signatures of spin-incoherent physics.

Contribution

It provides a theoretical analysis of spin-incoherent Luttinger liquids interacting with ferromagnets and superconductors, identifying observable signatures distinguishing them from conventional Luttinger liquids.

Findings

Temperature dependence of spin pumping differs in spin-incoherent regime

Magnetization dynamics reveal spin-incoherent behavior

Josephson currents show distinctive signatures of spin-incoherence

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 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 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 renormlized 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 current for a wire geometry in the limit of tunnel coupled superconductors. Both the ac and dc response contain "smoking gun" signatures that can be used to identify spin-incoherent behavior. Experimental requirements for the observation of these effects are laid out.