Observation of spin-splitting torque in altermagnets CrSb

Abstract Altermagnets can enable the unique nonrelativistic noncollinear spin current via spin splitting bands. However, this requires specific crystal symmetry paired spin-momentum locking, which is exclusively satisfied in d-wave but not g-wave altermagnets, significantly limiting the material candidate for efficient spin sources. In this work, we employ strain engineering to design the required crystal symmetry for symmetry-controlled spin current generation in g-wave altermagnets and experimentally realize it in chromium antimonide (CrSb). In pristine g-wave CrSb, the net spin current is cancelled by C_3-paired spin textures and hence the breaking C_3 symmetry can effectively transform pristine g-wave CrSb into a d-wave-like state. In this state, the alternating spin splitting bands emerge within the spin splitting plane defined by two main axes, [0001] and [101 ̅0] directions, enabling efficient interconversion between charge and spin currents along these axes. By resolving all three spin polarization components of the current-induced spin current and varying the current directions relative to the crystal orientations, we demonstrate the emergence of spin current in the spin splitting plane, with the spin polarization aligned with the Néel vector. Our findings establish strain as a powerful tool for symmetry engineering and spin current generation beyond d-wave systems, laying the groundwork for g-wave altermagnets as efficient spin sources and spin detectors.