Effects of disorder on electron heating in ultracold plasmas

Abstract

Starting from the beginning of their research in the early 2000s, the ultracold plasmas were considered as a promising tool to achieve considerable values of the Coulomb coupling parameter for electrons. Unfortunately, this was found to be precluded by a sharp spontaneous increase in temperature, which was often attributed to the so-called disorder-induced heating. It is the aim of the present paper to quantify the effect of spontaneous heating as a function of the initial ionic disorder and, thereby, to estimate the efficiency of its mitigation, e.g., by the Rydberg blockade. As a result of the performed simulations, we found that the dynamics of electrons exhibited a well-expressed transition from the case of the quasi-regular arrangement of ions to the disordered one; the magnitude of the effect being about 30%. Thereby, we can conclude that the two-step formation of ultracold plasmas—involving the intermediate stage of the blockaded Rydberg gas—can really serve as a tool to increase the degree of Coulomb coupling, but the efficiency of this method is moderate.