Coupling-energy driven pumping through quantum dots: the role of coherences

TL;DR

This paper investigates how off-resonant tunneling and quantum coherences influence electron pumping in quantum dots, focusing on two setups driven by coupling energy modulations, deriving exact solutions and identifying optimal conditions.

Contribution

It provides exact solutions for strong tunnel couplings without Coulomb interaction and compares two different quantum dot pumping mechanisms.

Findings

Identifies parameter regimes with maximum pumping current

Determines conditions for optimal energy efficiency

Analyzes similarities between different pumping mechanisms

Abstract

We study the impact of off-resonant tunneling and coherences on the electron pumping through quantum dots. Thereby, we focus on two electron-pump setups where lowest-order tunneling processes are suppressed and the pump is exclusively driven by modulations of the coupling energy. The first setup is driven by switching on and off the couplings between the quantum dot and the leads, while the second setup employs measurements of the dot occupation. We derive exact solutions for arbitrarily strong tunnel couplings in the absence of Coulomb interaction, identify parameter regimes with optimal pumping currents or optimal energy efficiency, and discuss similarities between both pumping mechanisms.