Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA.
Institute of Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest 1121, Hungary.
Phys Rev E. 2019 Dec;100(6-1):063206. doi: 10.1103/PhysRevE.100.063206.
A many-body system of charged particles interacting via a pairwise Yukawa potential, the so-called Yukawa one-component plasma (YOCP), is a good approximation for a variety of physical systems. Such systems are completely characterized by two parameters: the screening parameter, κ, and the nominal coupling strength, Γ. It is well known that the collective spectrum of the YOCP is governed by a longitudinal acoustic mode, both in the weakly and strongly coupled regimes. In the long-wavelength limit, the linear term in the dispersion (i.e., ω=sk) defines the sound speed s. We study the evolution of this latter quantity from the weak- through the strong-coupling regimes by analyzing the dynamic structure function S(k,ω) in the low-frequency domain. Depending on the values of Γ and κ and w=s/v_{th} (i.e., the ratio between the phase velocity of the wave and the thermal speed of the particles), we identify five domains in the (κ,Γ) parameter space in which the physical behavior of the YOCP exhibits different features. The competing physical processes are the collective Coulomb-like versus binary-collision-dominated behavior and the individual particle motion versus quasilocalization. Our principal tool of investigation is molecular dynamics (MD) computer simulation from which we obtain S(k,ω). Recent improvements in the simulation technique have allowed us to obtain a large body of high-quality data in the range Γ={0.1-10000} and κ={0.5-5}. The theoretical results based on various models are compared in order to see which one provides the most cogent physical description and the best agreement with MD data in the different domains.
一个由带电粒子通过双体 Yukawa 势相互作用组成的多体系统，即所谓的 Yukawa 单组分等离子体 (YOCP)，是许多物理系统的良好近似。这些系统完全由两个参数来描述：屏蔽参数 κ 和标称耦合强度 Γ。众所周知，在弱耦合和强耦合 regimes 下，YOCP 的集体谱都由一个纵向声模所支配。在长波极限下，色散的线性项（即 ω=sk）定义了声速 s。我们通过分析低频域中的动态结构函数 S(k,ω)，从弱耦合到强耦合 regime 来研究这个量的演化。取决于 Γ 和 κ 的值以及 w=s/v_{th}（即波的相速度与粒子的热速度之比），我们在 (κ,Γ) 参数空间中识别出了五个区域，其中 YOCP 的物理行为表现出不同的特征。竞争的物理过程是集体库仑型与二元碰撞主导型行为，以及个体粒子运动与准局域化行为。我们的主要研究工具是分子动力学 (MD) 计算机模拟，从中我们获得了 S(k,ω)。模拟技术的最新改进使我们能够在 Γ={0.1-10000} 和 κ={0.5-5} 的范围内获得大量高质量的数据。我们比较了基于各种模型的理论结果，以确定哪一个提供了最有说服力的物理描述，并在不同的区域与 MD 数据具有最好的一致性。
