Quantum pumping: Coherent Rings versus Open Conductors

TL;DR

This paper compares adiabatic quantum pumping in closed rings and open conductors, revealing a paradox where pumped current persists in open systems even with zero transmission, unlike in closed rings.

Contribution

It clarifies the underlying physics of quantum pumping in different geometries and resolves the paradoxical behavior observed in open conductors.

Findings

Pumped current in open conductors remains non-zero at zero transmission.

In closed rings, the pumped current vanishes as transmission approaches zero.

The underlying physics of adiabatic pumping is consistent across geometries.

Abstract

We examine adiabatic quantum pumping generated by an oscillating scatterer embedded in a one-dimensional ballistic ring and compare it with pumping caused by the same scatterer connected to external reservoirs. The pumped current for an open conductor, paradoxically, is non-zero even in the limit of vanishing transmission. In contrast, for the ring geometry the pumped current vanishes in the limit of vanishing transmission. We explain this paradoxical result and demonstrate that the physics underlying adiabatic pumping is the same in open and in closed systems.