Journal Article Research Support, Non-U.S. Gov't 1D tetrahedral networks 2D materials Metals SrFeO2.5 Zhang-Rice singlet states Zhang-Rice triplet states atomic stacking ferroelectricity intrinsic spin‐orbit torque and spintronics inversion symmetry breaking iron germanium telluride magnetoelectric coupling multiferroic van der Waals NiI2 multiferroicity nanogenerators optical absorption piezoelectricity possible van der Waals polar metals quantum entanglement second harmonic generation second-harmonic generation topological bands tungsten diselenide