Anomalous transport properties of the antiferromagnetic Weyl semimetals Mn3 X (X = Sn, Ge)

Noncollinear antiferromagnets Mn3 X (X = Sn, Ge) are characterized by a large anomalous Hall effect originating from a large Berry curvature despite a vanishingly small magnetization. From recent first-principle theories, the large Berry curvature is predicted to be induced by a existence of Weyl nodes broken time-reversal symmetry. The large anomalous Nernst effect is also contributed by the magnetic Weyl state around the Fermi level EF, and likely shares its origin with the anomalous Hall effect. The thermoelectric transport S(T) and thermomagnetic transport Sji(T) are thus investigated in single crystals of Mn3 X. Here, Mn3 X exhibits a large anomalous Nernst effect; in particular, the signal magnitude of Mn3Ge exceeds 1μV/K, which is 1.5 times that of Mn3Sn. The Weyl properties are discussed by analyzing the thermal conductivity, specific heat, and Seebeck and Nernst effects. We also evaluate the zero-field Nernst-driven thermoelectric figure of merit for device applications in the antiferromagnets Mn3 X.