Influence of dephasing and B/N doping on valley Seebeck effect in zigzag graphene nanoribbons

Abstract

We investigate the dephasing effect and atomic doping effect of random substitutional boron (B) or nitrogen (N) on the valley Seebeck effect in zigzag graphene nanoribbons (ZGNRs) using the tight-binding model calculations. When thermal gradient applied in the device made of ZGNRs is around several hundreds K, dephasing effect can only reduce the magnitude of pure valley current without generating electric current associated with the valley Seebeck effect. In the presence of B/N dopants, valley-polarized current occurs in ZGNRs. It is found that the generated valley polarized current is linearly dependent on the temperature gradient (ΔT) when the temperature of one lead is fixed and shows nonlinear dependence on temperature of a particular lead when ΔT is fixed. By calculating the phase diagrams such as (ΔT,p) with p the doping concentration, we find that the valley polarization can be tuned in a wide range from zero up to 0.72, indicating that it can be well controlled by B/N doping concentration. Finally, the noise power of valley Seebeck effect is also studied providing important information on the fluctuation of valley polarized current.