Exposing fractional spin excitations with spin current noise in one-dimensional quantum magnets

We theoretically study the spin current and its dc noise in the bulk of a XXZ spin-1/2 antiferromagnetic chain downstream of a weak potential barrier. The system is perturbed by the potential at a single point, thermalized throughout to a finite temperature, and driven at one end by a spin Hall-facilitated injection of spin excitations. We examine the spin Fano factor, defined as the spin current noise-to-signal ratio, for evidence of the fractional nature of the spin excitation hosted by the chain, and propose non-invasive methods of generating the potential and of measuring the bulk spin current and noise.