Electromechanical control of spin-Seebeck effects in armchair graphene nanoribbons

This study investigates the electronic and thermoelectric properties of a periodic structure of twisted armchair graphene nanoribbons (TAGNRs). We consider three different widths for TAGNRs based on N dimer chains (N=3p+q, where q=mod (N,3)) with and without vacancy defects. In ideal TAGNRs, by increasing the torsion coefficient, the bandgap decreases for q=1 and significantly increases for q=2 and q=0 in the low torsion regime, similar to local twists in these structures. When introducing vacancy defects, the mean field Hubbard model predicts a spin-semiconducting effect in all classes of TAGNRs. A giant spin Seebeck coefficient (SSC) is observed with a large bandgap in defected TAGNRs by tuning the twisting effect and the width of the nanoribbon. Generally, the SSC value and spin currents strongly depend on the torsion coefficient, the location of vacancy defects, and the width of the nanoribbon. Finally, the electromechanical behavior of AGNRs can manipulate the thermoelectric properties especially the SSC in the presence of vacancy defects.