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

In the present work we theoretically study characteristics of nonlinear Seebeck effect in a single-molecule junction with chain-like bridge of an arbitrary length. We have employed tight-binding models to compute electron transmission trough the system. We concentrate on 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 linear response regime.