Emergent d‑Wave Altermagnetism in Orthogonally Twisted Bilayer CrPS4.

Twistronics is a powerful strategy to engineer novel quantum states by controlling the relative orientation between layered materials. Here, we demonstrate that an orthogonally twisted bilayer CrPS4 shows d-wave altermagnetism driven purely by structural rotation. Symmetry analysis reveals that the 90° twisted stacking breaks the combined inversion and time-reversal symmetry, leading to an in-plane 2-fold rotation operation connecting opposite spin sublattices, enabling altermagnetism. First-principles calculations demonstrate a sizable nonrelativistic spin splitting of up to 68 meV around the Fermi level. Additionally, we show that the altermagnetic state can be further stabilized through interlayer compression and modulation of the on-site Coulomb interaction. The resulting band structure exhibits pronounced spin-dependent anisotropy, enabling efficient spin to charge conversion reaching ∼50% near the Fermi level and sizable giant magnetoresistance. These results establish twisted CrPS4 as a realistic platform for altermagnetism and highlight twistronics as a versatile route for advanced spintronics applications.