Influence of external temperature gradient on acoustoelectric current in   graphene
  Recent analyses of thermoelectric amplification of acoustic phonons in Free-Standing Graphene (FSG) $\Gamma_q^{grap}$ have prompted the theoretical study of the influence of external temperature gradient ($\nabla T$) on the acoustoelectric current $j_T^{(grap)}$ in FSG. Here, we calculated thermal field on open circuit ($j_T^{(grap)} = 0$) to be $(\nabla T)^g = 746.8Km^{-1}$. We then calculated acoustoelectric current ($j_T^{(grap)}$)to be $1.1mA\mu m^{-2}$ for $\nabla T = 750.0 Km^{-1}$, which is comparable to that obtained in semiconductors ($1.0mA\mu m^{-2}$), the thermal-voltage $(V_T)_0^g$ to be $6.6\mu V$ and the Seebeck coefficient $S$ as $8.8\mu V/K$. Graphs of the normalized $j_T^{(grap)}/j_0$ versus $\omega_q$, $T$ and $\nabla T/T$ were sketched. For $j_T^{(grap)}$ on $T$ for varying $\omega_q$, Negative Difference Conductivity (NDC) ($| \frac{\partial j}{\partial T}| < 0$) was observed in the material. This indicates graphene is a suitable material for developing thermal amplifiers and logic gates. 
K. A. Dompreh, N. G. Mensah, S. Y. Mensah and R. Edziah
cond-mat.mes-hall