Operating a quantum pump in a closed circuit

TL;DR

This paper analyzes quantum pumps in closed circuits, revealing that they can transfer more charge per cycle than previously expected, using advanced theoretical tools like the Kubo formula and Dirac chains.

Contribution

It provides a detailed theoretical analysis showing that quantum pumps in closed circuits can transfer charge exceeding the elementary charge, challenging prior assumptions.

Findings

Quantum pumps can transfer charge greater than e in closed circuits.

The Kubo formula and Dirac chains are effective tools for analyzing quantum pumping.

Practical estimates for transferred charge are derived from the theoretical framework.

Abstract

During an adiabatic pumping cycle a conventional two barrier quantum device takes an electron from the left lead and ejects it to the right lead. Hence the pumped charge per cycle is naively expected to be $Q \le e$. This zero order adiabatic point of view is in fact misleading. For a closed device we can get ${Q > e}$ and even ${Q \gg e}$. In this paper a detailed analysis of the quantum pump operation is presented. Using the Kubo formula for the geometric conductance, and applying the Dirac chains picture, we derive practical estimates for~$Q$.