Dephasing at Low Temperatures

TL;DR

This paper examines the mechanisms of quantum dephasing at low temperatures, emphasizing the roles of zero point fluctuations and thermal noise, and discusses the limitations of semiclassical models in this regime.

Contribution

It provides a detailed analysis of dephasing contributions at low temperatures and proposes modifications to existing semiclassical approaches.

Findings

Zero point fluctuations become irrelevant for thermal motion at low temperatures.

The white noise approximation is valid at high temperatures but limited at low temperatures.

Limitations of semiclassical models are identified and addressed.

Abstract

We discuss the significance and the calculation of dephasing at low temperatures. The particle is moving diffusively due to a static disorder configuration, while the interference between classical paths is suppressed due to the interaction with a dynamical environment. At high temperatures we may use the `white noise approximation' (WNA), while at low temperatures we distinguish the contribution of `zero point fluctuations' (ZPF) from the `thermal noise contribution' (TNC). We study the limitations of the above semiclassical approach and suggest the required modifications. In particular we find that the ZPF contribution becomes irrelevant for thermal motion.