Nonlinear thermovoltage and thermocurrent in quantum dots

TL;DR

This paper investigates the nonlinear thermoelectric effects in quantum dots embedded in nanowires, revealing how thermal bias influences energy levels and proposing a model that includes Kondo correlation melting, with implications for energy conversion efficiency.

Contribution

It introduces a theoretical model accounting for energy level renormalization due to thermal bias and links it to Kondo correlation melting in quantum dots.

Findings

Nonlinear thermovoltage and thermocurrent observed in quantum dots.

Renormalization of quantum-dot energy levels explains nonlinear effects.

Kondo correlation melting contributes to energy level shifts.

Abstract

Quantum dots are model systems for quantum thermoelectric behavior because of the ability to control and measure the effects of electron-energy filtering and quantum confinement on thermoelectric properties. Interestingly, nonlinear thermoelectric properties of such small systems can modify the efficiency of thermoelectric power conversion. Using quantum dots embedded in semiconductor nanowires, we measure thermovoltage and thermocurrent that are strongly nonlinear in the applied thermal bias. We show that most of the observed nonlinear effects can be understood in terms of a renormalization of the quantum-dot energy levels as a function of applied thermal bias and provide a theoretical model of the nonlinear thermovoltage taking renormalization into account. Furthermore, we propose a theory that explains a possible source of the observed, pronounced renormalization effect by the melting of Kondo correlations in the mixed-valence regime. The ability to control nonlinear thermoelectric behavior expands the range in which quantum thermoelectric effects may be used for efficient energy conversion.