Polarons in 2+epsilon dimensions and giant figure of merit of semiconducting nanolayers

Abstract

Polarons - electrons coupled with lattice vibrations - play a key role in the transport and optical properties of many systems of reduced dimension and dimensionality. Their confinement affects drastically the phonon, polaron, bipolaron and multi-polaron properties of quantum wells. Here we calculate the energy spectrum and thermopower of polarons confined to a potential well as a function of the well thickness. We show that the polaron mass enhancement in 2+epsilon dimensions explains a giant thermolectric power recently observed in doped semiconducting nanolayers (multiple quantum wells (MQWs)), and propose a route for enhancing the performance of thermoelectric energy nanoconverters increasing their figure of merit by more than one order of magnitude.