Exploring spin transport and piezoelectricity in flexible 2D V₂STeO altermagnets

Altermagnets (AMs) herald a transformative paradigm and provide a promising pathway for energy-efficient spintronics, harnessing symmetry-protected spin polarization without net magnetization. In this study, we investigate the two-dimensional (2D) V₂STeO altermagnetic system using first-principles calculations. V₂STeO exhibits a direct band gap of 0.43 eV and a sizable intrinsic spin splitting of 1.14 eV. We obtain a relatively high Néel temperature of 475 K. Under hole doping (μ ≈ -0.80 eV), the spin Hall conductivity reaches +70 (ℏ/e) (S m^-1), indicating efficient charge-to-spin conversion. Nonetheless, the spin Seebeck coefficient of 0.72 mV K^-1 suggests better thermal-to-spin conversion. The quantitative (Bader) and qualitative (Born-effective) charge analyses reveal an asymmetric distribution that induces an out-of-plane dipole and an internal electric field, which in turn breaks inversion symmetry and facilitates polarization under mechanical perturbation (stress/strain). Moreover, V₂STeO displays mechanical flexibility and an out-of-plane piezoelectric response, characterized by a strain coefficient of d₃₁ = -0.355 pm V^-1. Consequently, these results suggest that V₂STeO could be a candidate for spintronics, spin-caloritronics, and flexible piezotronics applications.