Nonlinear Electronic Density Response in Warm Dense Matter

用置换阻塞路径积分蒙特卡罗方法研究热稠密电子气的静态密度响应

Permutation Blocking Path Integral Monte Carlo approach to the Static Density Response of the Warm Dense Electron Gas

均匀电子气的静态密度响应对于许多应用是至关重要的。在这里，我们采用最近开发的\textit{ab initio}置换阻塞路径积分蒙特卡罗（PB-PIMC）技术[T.~ Dornheim \textit{et al.}，\textit{New J.~Phys.} ~ \textbf{17}，073017（2015）]，以在温暖的致密物质条件下进行谐波扰动电子气的广泛模拟。特别是，我们详细调查的线性响应理论的有效性，并证明PB-PIMC允许获得高度准确的结果的静态密度响应函数，因此，静态局部场校正。我们的新\textit{ab initio}数据与介电近似的比较揭示了需要精确处理相关性。最后，我们考虑了多重扰动的叠加，并讨论了静态响应函数的计算的影响。

热稠密电子气静态结构因子的\textit{Ab Initio}结果

\textit{Ab Initio} results for the Static Structure Factor of the Warm Dense Electron Gas

有限温度下的均匀电子气是当前研究热稠密物质的热点。量子简并和库仑耦合效应的复杂相互作用完全包含在对分布函数中，或者等价地，静态结构因子中。通过结合精确的量子Monte Carlo结果的长波矢量的长期行为从Singwi-Tosi-Land-Sjölander近似，我们能够获得高精度的数据的静态结构因子在整个$k$范围。这使我们能够衡量以前的近似的准确性，并讨论各自的缺点。此外，我们的新数据将为其他量的计算提供有价值的输入。

激发态的有限温度格林函数方法和冷变暖稠密物质的热力学性质

Finite temperature Green's function approach for excited state and thermodynamic properties of cool to warm dense matter

本文提出了一种有限温度下延拓的延迟累积格林函数，用于计算电子系统的激发态和热力学性质。与多体微扰理论的$GW$近似相比，该方法在屏蔽库仑相互作用$W$中引入了一个累积量，改善了激发态的性质。均匀电子气的结果提出了一个广泛的密度和温度范围内，从冷到温暖的致密物质制度，揭示了一些迄今意想不到的属性。例如，在高$T$时，相关效应保持强，而交换相关能变小。此外，随着温度的升高，谱函数变宽，阻尼增加，模糊了通常的准粒子图像。类似地，康普顿散射表现出在正常密度和中间$T$下持续存在的大量多体修正。交换相关能和交换相关势的计算结果与现有理论和有限温度DFT泛函的计算结果吻合较好。

Momentum distribution functions and pair correlation functions of unpolarized uniform electron gas in warm dense matter regime

In this paper we continued our research of the uniform electron gas, using the single--momentum path integral Monte Carlo method, and studied the momentum distribution functions and the pair correlation functions in the warm dense matter regime. We discovered that the single--particle momentum distribution function deviates from the Fermi distribution and forms so-called "quantum tails" at high momenta, if non-ideality is strong enough in both degenerate and non-degenerate cases. This effect is always followed by the appearance of the short--range order on the pair distribution functions and c…

\textit{Ab Initio} Path Integral Monte Carlo Results for the Dynamic Structure Factor of Correlated Electrons: From the Electron Liquid to Warm Dense Matter

The accurate description of electrons at extreme density and temperature is of paramount importance for, e.g., the understanding of astrophysical objects and inertial confinement fusion. In this context, the dynamic structure factor $S(\mathbf{q},ω)$ constitutes a key quantity as it is directly measured in X-ray Thomson (XRTS) scattering experiments and governs transport properties like the dynamic conductivity. In this work, we present the first \textit{ab initio} results for $S(\mathbf{q},ω)$ by carrying out extensive path integral Monte Carlo simulations and developing a new method for the …

位形路径积分蒙特卡罗方法研究温密电子气的静态密度响应

Configuration Path Integral Monte Carlo Approach to the Static Density Response of the Warm Dense Electron Gas

均匀电子气（UEG）的静态密度响应函数（SDRF）的精确知识作为许多应用的关键输入，最重要的是超越广义梯度近似的密度泛函理论。在这里，我们扩展的配置路径积分蒙特卡罗（CPIMC）的形式主义，以前适用于空间均匀的电子气的情况下，通过添加一个空间周期性的外部电位的非均匀电子气。该过程最近已成功地用于热稠密电子气的置换阻塞路径积分蒙特卡罗模拟（PB-PIMC）[Dornheim \textit{et al.}，Phys. Rev. Ein press，arXiv：1706.00315]，但该方法仅限于低密度和中等密度。在CPIMC中实现这一过程使我们能够获得精确的有限温度结果，为电子气体的SDRF在\textit{high to moderate densities}关闭的差距留下开放的PB-PIMC数据。在本文中，我们演示了如何CPIMC形式主义可以有效地扩展到空间不均匀的电子气，并提出了第一个数据点。最后，我们详细讨论了SDRF的量子Monte Carlo结果中涉及的有限尺寸误差，并提出了一种基于基态技术推广的消除这些误差的方法。

The Static Local Field Correction of the Warm Dense Electron Gas: An ab Initio Path Integral Monte Carlo Study and Machine Learning Representation

The study of matter at extreme densities and temperatures as they occur in astrophysical objects and state-of-the art experiments with high-intensity lasers is of high current interest for many applications. While no overarching theory for this regime exists, accurate data for the density response of correlated electrons to an external perturbation are of paramount importance. In this context, the key quantity is given by the local field correction (LFC), which provides a wave-vector resolved description of exchange-correlation effects. In this work, we present extensive new path integral Mont…

Density Response of the Warm Dense Electron Gas beyond Linear Response Theory: Excitation of Harmonics

In a recent Letter, Dornheim et al. [PRL 125, 085001 (2020)] have investigated the nonlinear density response of the uniform electron gas in the warm dense matter regime. More specifically, they have studied the cubic response function at the first harmonic, which cannot be neglected in many situations of experimental relevance. In this work, we go one step further and study the full spectrum of excitations at the higher harmonics of the original perturbation based on extensive new ab initio path integral Monte Carlo (PIMC) simulations. We find that the dominant contribution to the density res…

The Uniform Electron Gas at Warm Dense Matter Conditions

We review the uniform electron gas (UEG) at finite temperature and over a broad density range relevant for warm dense matter (WDM) applications. We provide an overview of different simulation techniques, focusing on recent developments in the dielectric formalism and quantum Monte Carlo (QMC). Our primary focus is on two novel QMC methods: Permutation blocking path integral MC (PB-PIMC) and configuration PIMC (CPIMC). In fact, a combination of PB-PIMC and CPIMC has allowed for a highly accurate description of the warm dense UEG over a broad density-temperature range. We are able to effectively…

暖密铝中均匀电子气模型破裂的实验证据

Experimental Evidence for the Breakdown of Uniform-Electron-Gas Models in Warm Dense Aluminium

研究通过实验表明，均匀电子气模型在暖密铝中无法准确描述等离子体共振，需采用从头计算方法以可靠推断热力学条件。