Inverse Altermagnetic Spin Splitting Effect‐Induced Terahertz Emission in RuO₂

Abstract

The relativistic inverse spin Hall effect (ISHE) plays a pivotal role in terahertz (THz) emission in magnet/heavy metal bilayers. Here, THz emission from RuO2/Py bilayers is reported due to not only the relativistic ISHE but also the nonrelativistic inverse altermagnetic spin splitting effect (IASSE) in RuO2. For the (100)‐oriented RuO2/Py bilayers, the THz emission is greatly enhanced owing to IASSE once the polarization direction of the spin current (from the Py layer induced by pump laser) is parallel to the Néel vector of RuO2, producing the anisotropic THz emission with twofold symmetry. In contrast, the RuO2(110)/Py bilayer only exhibits isotropic THz emission because of the absence of IASSE‐induced spin‐charge conversion in the (110)‐oriented RuO2 films. Apart from the fundamental significance of exploring the IASSE‐induced spin‐to‐charge conversion, the finding also enriches the physical mechanism and modulation method of THz emission in spintronic systems.

Altermagnetic surface states: towards the observation and utilization of altermagnetism in thin films, interfaces and topological materials

“…For instance, the AM is preserved on the surface (110) of RuO 2 as also shown in recent experiments. 50 In the case of alternate positions along all directions of the R 1 and R 2 points as in the C-type of YVO 3 perovskite, 30 the altermagnetic surface states will be observable on the (110), (101), (011) and (111) surfaces while all principal surface orientations will be blind to the AM.…”

“…Regarding technological applications, altermagnets may assume a leading role in realizing concepts in spincaloritronics, 22 THz emissions in spintronic systems, 23 THz spin current dynamics in g-wave altermagnet hematite 24 and an efficient spin-charge conversion. 25 Furthermore, they can be used in Josephson junctions 26 and to generate neutral currents for spintronics.…”

Observation of Giant Spin Splitting and d-wave Spin Texture in Room Temperature Altermagnet RuO2

“…This substantial spin splitting in RuO 2 is of great scienti c interest and has a wide range of potential uses. Novel observations in RuO 2 include the reporting of anomalous Hall effect and in-plane Hall effect [40][41][42][43] , along with the prediction of giant and tunneling magnetoresistance [44][45][46] , the identi cation of titled spin currents and crystal thermal transport 47,48 , and the documentation of terahertz emission induced by spin splitting effect 49,50 .…”

Emerging Antiferromagnets for Spintronics

“…Similar to the case of antiferromagnetic domain‐wall devices, the studies on antiferromagnetic THz emitters are also at a very initial stage. Hitherto, antiferromagnets have been employed as either the spin‐current generator [ 167 ] or the spin‐charge converter [ 168–170 ] in such devices, which have demonstrated the ultrafast dynamics of spin‐current generation and spin‐charge conversion process, respectively.…”