Unusual thermoelectric properties of BaFe2As2 in high magnetic fields

Abstract

Electric and thermoelectric transport properties are mutually intertangled in diffusive transport equations. In particular, in high mobility multiband systems an anomalous behavior may occur, which can be tracked down to the properties of the individual bands. Here, we present magnetoelectric and magnetothermoelectric transport properties of a ${\mathrm{BaFe}}_{2}{\mathrm{As}}_{2}$ high-quality single crystal, for different magnetic field directions up to 30 T. We detect a giant Nernst effect and an anomalous field dependence of the Seebeck coefficient. The extraction of the Peltier tensor coefficients ${\ensuremath{\alpha}}_{xx}, {\ensuremath{\alpha}}_{xy}$, and ${\ensuremath{\alpha}}_{xz}$ allows us to disentangle the main transport mechanisms in play. The large ${\ensuremath{\alpha}}_{xy}$ and ${\ensuremath{\alpha}}_{xz}$ values and their field dependence provide evidence of the presence of a high mobility band, compatible with a Dirac dispersion band, crossing the Fermi level, and suggest a possible three-dimensional nature of the Dirac fermions.