Altermagnets constitute a recently identified magnetic phase that combines the absence of macroscopic magnetization, characteristic of antiferromagnets, with the spin splitting typically associated with ferromagnets. This hybrid nature enables stray-field-free spin transport and ultrafast spin dynamics, offering new opportunities for dissipationless spintronics and spin-caloritronics. Here, we perform a comprehensive symmetry analysis and advanced first-principles calculations to investigate the intrinsic spin Hall and spin Nernst effects in two-dimensional altermagnets, using bilayer MnPSe3 as a representative example. In the nonrelativistic limit, interlayer sliding induces a d-wave-like spin splitting and generates time-reversal-odd, intraband-dominated spin Hall and spin Nernst responses. Changing the sliding direction alters the associated symmetry operations, thereby modifying the spin splitting of the Fermi surface and enabling tunable control of spin-transport properties. This modulation originates from symmetry-driven variations in the relative contributions of opposite spins. Our findings identify interlayer sliding as an effective route to tuning spin transport in altermagnets, establishing a versatile two-dimensional platform for exploring the interplay between altermagnetism and spin transport, and paving the way for future advances in altermagnetic spintronics and spin-caloritronics.
Liu et al. (2026) studied this question.