Design of spin-Seebeck diode with spin semiconductors

We report a new design of spin-Seebeck diode using two-dimensional spin semiconductors such as sawtooth-like (ST) silicence nanoribbons (SiNRs), to generate unidirectional spin currents with a temperature gradient. ST SiNRs have subbands with opposite spins across the Fermi level and hence the flow of thermally excited carriers may produce a net spin current but not charge current. Moreover, we found that even-width ST SiNRs display a remarkable negative differential thermoelectric resistance due to a charge-current compensation mechanism. In contrast, odd-width ST SiNRs manifest features of a thermoelectric diode and can be used to produce both charge and spin currents with temperature gradient. These findings can be extended to other spin semiconductors and open the door for designs of new materials and spin caloritronic devices.