Orientation-dependent THz emission in non-collinear antiferromagnetic Mn3Sn and Mn3Sn-based heterostructures

We observe terahertz (THz) emission in Mn3Sn, Mn3Sn/Pt, and Mn3Sn/Co films excited by a femtosecond laser pulse. In the Mn3Sn film and Mn3Sn/Pt heterostructures, the THz emission originates from both magnetic-dipole and superdiffusive transient spin current with different proportions. Our results unambiguously demonstrate that THz emission can be controlled by the spin structure of Mn3Sn. The (0001)-orientated Mn3Sn produces stronger THz emission than the (112¯0)-orientated counterpart because for the latter one, only half of the kagome planes of Mn3Sn are parallel to the field, which can be controlled by the external magnetic field. In the Mn3Sn/Co heterostructure, the Mn3Sn layer serves as a spin-to-charge converter. The (112¯0)-orientated Mn3Sn emits larger THz signals than (0001)-orientated Mn3Sn due to the anisotropic inverse spin Hall effect, determined by the relative relation between spin, charge current, and the kagome plane of Mn3Sn. The spin structure dependent THz radiations in noncollinear antiferromagnetic metal Mn3Sn provide versatility for both spintronics and THz optics.