  We study the phenomenon of spin-current rectification in a one-dimensional
XXZ spin chain in the presence of a thermal drive. In our model a pure spin
current is generated by a temperature difference between two harmonic heat
baths which in turn creates a spin voltage via the spin-Seebeck effect. Along
with a local spin-current operator definition and the nonequilibrium modified
Redfield solution we study the spin-rectification ratio as a function of system
size and external magnetic field. Intriguing effects are observed at low
temperatures such as oscillations with system size and high range of tunability
with external magnetic field making magnetic insulators, which are well
described by the XXZ model, ideal candidates to build spin devices based on
rectification.
