Altermagnet-Driven Magnon Spin Splitting Nernst Effect

Magnonic spin current generation in antiferromagnets has emerged as an important topic in spintronics, where a strong external magnetic field or a Dzyaloshinskii-Moriya interaction (DMI) is generally required. Recently, a type of antiferromagnets characterized by momentum-dependent nonrelativistic spin splitting bands, referred to as altermagnets, has offered an unprecedented approach to generating magnon spin current without the constraints of a magnetic field or DMI. Here, we demonstrate the magnon spin splitting Nernst effect (MSSNE) in the LuFeO_{3} films, where applying a longitudinal temperature gradient generates a transverse magnonic spin current. Four critical types of evidence support the observed MSSNE originating from the spin splitting of magnon bands, as further corroborated by the symmetry analysis, rather than the DMI. Our findings not only demonstrate the MSSNE but also highlight the intriguing magnonic properties in the altermagnets, which have emerged as a promising material platform for antiferromagnetic spintronic applications.