Negative Echo in the Density Evolution of Ultracold Fermionic Gases

TL;DR

This paper predicts a nonequilibrium negative echo phenomenon in the density evolution of ultracold fermionic gases, which can serve as an experimental marker for the superfluid transition point.

Contribution

It introduces the concept of a negative echo in density evolution as a new critical phenomenon in ultracold fermionic gases above the superfluid transition temperature.

Findings

Negative echo observed on the BCS side of the crossover.

Echo dominates over bosonic spreading at large times.

Potential use as an experimental transition marker.

Abstract

We predict a nonequilibrium critical phenomenon in the space-time density evolution of a fermionic gas above the temperature of transition into the superfluid phase. On the BCS side of the BEC-BCS crossover, the evolution of a localized density disturbance exhibits a negative echo at the point of the initial inhomogeneity. Approaching the BEC side, this effect competes with the slow spreading of the density of bosonic molecules. However, even here the echo dominates for large enough times. This effect may be used as an experimental tool to locate the position of the transition.