Electron trapping in freely expanding ultracold neutral plasmas

TL;DR

This paper investigates how electrons become self-trapped in expanding ultracold neutral plasmas, using theoretical modeling and simulations to understand the electrostatic potential and transient confinement effects.

Contribution

It introduces a theoretical model and molecular dynamics simulations to describe electron trapping and the transient Thomas-Fermi potential in ultracold plasmas.

Findings

Electron trapping occurs in freely expanding ultracold plasmas.

The plasma potential exhibits a Thomas-Fermi type in strong confinement.

Simulations confirm the transient nature of the Thomas-Fermi potential.

Abstract

We report on the self-induced electron trapping occurring in a ultracold neutral plasma that is set to expand freely. At the early stages of the plasma, the ions are not thermalized follow a Gaussian spatial profile, providing the trapping to the coldest electrons. In the present work, we provide a theoretical model describing the electrostatic potential and perform molecular dynamics simulations to validate our findings. We show that in the strong confinement regime, the plasma potential is of a Thomas-Fermi type, similar to the case of heavy atomic species. The numerically simulated spatial profiles of the particles corroborate this claim. We also extract the electron temperature and coupling parameter from the simulation, so the duration of the transient Thomas-Fermi is obtained.