Demonstrating Universal Scaling in Quench Dynamics of a Yukawa One-Component Plasma

The Yukawa one-component plasma (OCP) is a paradigm model for describing plasmas that contain one component of interest and one or more other components that can be treated as a neutralizing, screening background. In appropriately scaled units, interactions are characterized entirely by a screening parameter, $kappa$. As a result, systems of similar $kappa$ show the same dynamics, regardless of the underlying parameters (e.g., density and temperature). We demonstrate this behavior using ultracold neutral plasmas (UNP) created by photoionizing a cold ($Tle10$ mK) gas. The ions in UNP systems are well described by the Yukawa model, with the electrons providing the screening. Creation of the plasma through photoionization can be thought of as a rapid quench from $kappa_{0}=infty$ to a final $kappa$ value set by the electron density and temperature. We demonstrate experimentally that the post-quench dynamics are universal in $kappa$ over a factor of 30 in density and an order of magnitude in temperature. Results are compared with molecular dynamics simulations. We also demonstrate that features of the post-quench kinetic energy evolution, such as disorder-induced heating and kinetic-energy oscillations, can be used to determine the plasma density and the electron temperature.