Aspects of quantum cooling in electron and atom systems

TL;DR

This paper investigates quantum cooling mechanisms in electron and atom systems, highlighting the limits of cooling power, effects of driving signals, and alternative cooling sources, with implications for quantum refrigeration technology.

Contribution

It introduces the quantum limit to cooling power in electron systems and explores quantum cooling in atom systems, including effects of different driving signals and thermal baths.

Findings

Inelastic reflection can cause heating with time-symmetric driving.

The quantum of cooling power sets an upper limit per transport channel.

Electron cooling persists with a hot thermal bath replacing the coherent source.

Abstract

Some features of nonadiabatic electron heat pumps are studied and connected to general questions of quantum cooling. Inelastic reflection is shown to contribute to heating if the external driving signal is time-symmetric. The quantum of cooling power, $\pi^2 k_B^2 T^2/6h$, is shown to be an upper limit to the cooling rate per transport channel in the presence of an arbitrary driving signal. The quantum limit to bulk atom cooling is also discussed. Within the electron tunneling limit, it is shown that electron cooling still occurs if the coherent ac source is replaced by a sufficiently hot thermal bath. A comparison with related refrigeration setups is presented.