Analyzing X-ray Thomson scattering experiments of warm dense matter in the imaginary-time domain: theoretical models and simulations

TL;DR

This paper introduces a semi-analytical model for imaginary-time correlation functions in warm dense matter, enabling model-free temperature diagnostics and improving understanding of physical properties in X-ray Thomson scattering experiments.

Contribution

It presents a new semi-analytical model for the imaginary-time dependence of two-body correlations, validated against ab initio simulations, enhancing interpretation of XRTS data.

Findings

Excellent agreement with path integral Monte Carlo results across various parameters

Model facilitates temperature diagnostics without relying on approximations

Provides insights into physical properties in the imaginary-time domain

Abstract

The rigorous diagnostics of experiments with warm dense matter (WDM) is notoriously difficult. A key method is given by X-ray Thomson scattering (XRTS), but the interpretation of XRTS measurements is usually based on theoretical models that entail various approximations. Recently, Dornheim et al. [arXiv:2206.12805] have introduced a new framework for temperature diagnostics of XRTS experiments that is based on imaginary-time correlation functions (ITCF). On the one hand, switching from the frequency- to the imaginary-time domain gives one direct access to a number of physical properties, which facilitates the extraction of the temperature of arbitrarily complex materials without any models or approximations. On the other hand, the bulk of theoretical works in dynamic quantum many-body theory is devoted to the frequency-domain, and, to our knowledge, the manifestation of physics properties within the ITCF remains poorly understood. In the present work, we aim to change this unsatisfactory situation by introducing a simple, semi-analytical model for the imaginary-time dependence of two-body correlations within the framework of imaginary-time path integrals. As a practical example, we compare our new model to extensive ab initio path integral Monte Carlo results for the ITCF of a uniform electron gas, and find excellent agreement over a broad range of wave numbers, densities, and temperatures.