Role of twist in modulating the electronic and thermoelectric properties of zigzag graphene nanoribbons

We investigate the electronic structure and Seebeck coefficient (SC) of twisted zigzag graphene nanoribbons (TZGNRs) with translational symmetry, considering electron-electron interactions, electric fields, and vacancy defects. Using the mean-field Hubbard model, we find that the semiconducting properties of TZGNRs in the antiferromagnetic ground state are preserved when twisted. However, the energy gap significantly decreases with shorter twist lengths. Unlike GNRs, electric fields, which do not induce spin-polarized features, can reduce the energy gap and SC, and cause a flattening of the band structure around the Fermi energy. The variation in the band energy depends on the twist length and electric field strength. Furthermore, monovacancy defects in TZGNRs induce spin-polarization effects in both the band structure and SC, depending on their spatial position within the nanoribbon structure. These versatile features of TZGNRs indicate their potential in stretchable electronics and thermoelectric applications.