Thermoelectric effect in kagome lattice enhanced at van Hove singularities

We have performed first-principles calculations using density functional theory on a kagome lattice model with a chiral spin state, as a representative example demonstrating significant longitudinal and transverse thermoelectric properties. The results revealed that the saddle-point-type van Hove singularity (VHS) enhances thermoelectric effects. The longitudinal thermoelectric conductivity $\alpha_{xx}$ was large at the chemical potentials tuned close to the band at the symmetry points, K (lower band edge), $\Gamma$ (upper band edge), and M (saddle point), where the VHSs of the density of states (DOS) were at the corresponding band energies. The transverse thermoelectric conductivity $\alpha_{xy}$ was large at the chemical potential of saddle-point-type VHS. A large anomalous Nernst coefficient of about 10 $\mu$V/K at 50 K was expected.