The thermoshape voltage induced by quantum shape effects

We propose here a new effect for the conversion of heat energy into electricity with nanostructures. We recently used size-invariant shape transformation to completely separate quantum size and shape effects from each other, which allows one to focus on purely quantum shape effects. In this work, we first present the existence of the quantum shape effects on thermoelectric transport properties of GaAs nanostructures at ballistic regime. Then we consider a junction composed of the same material having exactly the same geometric sizes, but distinct shapes. We show that an electric voltage is induced under a temperature gradient in such a junction because of the quantum shape effects on Seebeck coefficients. This cross effect is called the thermoshape effect. Our calculations based on Landauer formalism predict that the thermoshape voltage is persistent and in the order of mV/K for non-degenerate GaAs semiconductors. Our study explicitly suggests how important the effect of overall geometry is in nanoscale thermoelectric materials, and can be utilized even if all sizes are the same. A thermoshape junction not only represents a viable setup for the macroscopic manifestation of quantum shape effects, but also constitutes their first possible device application.