Length-dependent Seebeck effect in single-molecule junctions beyond linear response regime

In the present work, we theoretically study characteristics of the nonlinear Seebeck effect in a single-molecule junction with chain-like bridge of an arbitrary length. We have employed tight-binding models to compute the electron transmission through the system. We concentrate on the analysis of dependences of thermovoltage V_th and differential thermopower S on the bridge length. It is shown that V_th becomes stronger and S grows as the bridge lengthens. We discuss the effects of the bridge coupling to the electrodes and of specific characteristics of terminal sites on the bridge on the length-dependent V_th and S, which appear when the system operates beyond the linear response regime.