Thermoelectric Effect in Kagome Lattice Enhanced at Van Hove Singularities

We 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 αxx was large at the chemical potentials tuned close to the band at the symmetry points K (lower band edge), Γ (upper band edge), and M (saddle point), where the VHSs of the density of states were at the corresponding band energies. The transverse thermoelectric conductivity αxy was large at the chemical potential of the saddle-point-type VHS. A large anomalous Nernst coefficient of approximately 10 µV/K at 50 K was expected.