Fig. 7: THz emission from rotationally symmetric magnetic systems.

a THz emission from (110) NiO driven by a near-infrared ultrafast pulse via ISRS and (b) the corresponding Fourier transform. c THz emission from (111) NiO driven by a near-infrared ultrafast pulse via ISRS (upper panel) and corresponding Fourier transform (lower panel). d Six-fold rotational symmetry of \(x\)- (upper panel) and \(y\)-polarized (lower panel) THz field components from (111) NiO under sample rotation, where red lobes correspond to a positive signed transient and blue lobes correspond to a negative signed transient. e ISRS selection rules for colinear scattering where the upward blue arrow indicated photon annihilation, the downward orange arrow indicates photon creation, and the downward red arrow indicates magnon excitation. f Six-fold symmetric THz emission from (111) NiO/Pt heterostructure (left panel) and (111) NiO (right panel) under sample rotation showing dramatic enhancement in the heterostructure. g THz transients from NiO/Pt heterostructures with various NiO crystal faces (left panel) and corresponding bare NiO response. Panels (a) and (b) reprinted with permission from¹⁴³ © 2010 American Institute of Physics. Panels (c) and (d) reprinted from¹⁴⁴ © 2011 American Physical Society, under the terms of CC-BY 3.0. Panels (f) and (g) reprinted with permission from¹⁴⁵ © 2020 the Author(s), under exclusive licence to Springer Nature