Chirality-dependent spin transport and spin Seebeck effect in the spiral spin chains

The observation of spin Seebeck effect has triggered intense research in the spintronics. Especially, it is considered to be one alternative method to generate pure spin current in magnetic materials. Here, the spin Seebeck coefficient and the spin figure of merit are calculated by using Green's function method in the spiral spin chain with Dzyaloshinskii-Moriya interaction (DMI). The Zeeman-like effect and the similarity between the chirality and the spin in the spiral spin chain are revealed according to the dispersion relation. In addition, we find that the spin Seebeck coefficient and the spin figure of merit show peaks around the magnon spin transmission channel. In the absence of external magnetic field, the spin Seebeck peaks for opposite chirality are degenerated. However, the spin Seebeck peaks are chirality-dependent in the presence of magnetic field, and the spin Seebeck peaks with opposite chirality locate at different chemical potentials, leading to the energy difference between the spin Seebeck peaks with opposite chirality. Furthermore, the energy difference is determined by the magnetic field and the DMI, and the energy difference becomes larger for stronger DMI or higher magnetic field.