Two-Dimensional\nChiral Covalent Organic Frameworks\nwith Significant Rashba–Dresselhaus Spin Splitting

Two-dimensional (2D) nonmagnetic semiconductors with\nlarge Rashba–Dresselhaus\n(R-D) spin splitting hold promise for applications in electric-field-controlled\nspintronics. Current research primarily focuses on metal-based R-D\nmaterials. A natural question is whether significant R-D spin splitting\ncan be realized in metal-free organic systems. In this work, through\nfirst-principles calculations, we demonstrate that 2D chiral covalent\norganic frameworks (CCOFs) can serve as a potential platform for designing\nR-D semiconductors. By constructing 2D CCOFs with benzene cores and\niodine-based chiral linkers, significant spin splitting at the valence\nband is achieved. Particularly, with 2,2′-diiodobiphenyl linkers,\nthe R-D energy of spin splitting is 12 meV, accompanied by a coupling\nconstant (α) of 0.12 eVÅ. Meanwhile, the spin texture of\nthe valence band is adjustable via tuning the chirality. Furthermore,\nthrough group substitutions, the R-D energy can be notably increased\nup to 32 meV and the coupling constant up to 0.4 eVÅ, comparable\nto metal-based R-D materials.