Ab initio path integral Monte Carlo results for the dynamic and static density response of correlated electrons

Over the last decades, there has emerged a growing interest in warm dense matter (WDM), an exotic state with extreme densities and temperatures. These conditions are relevant for, e.g., the description of astrophysical objects and laser-excited solids, but a theoretical description is notoriously difficult.

In this work, we focus on the uniform electron gas (UEG), one of the most fundamental model systems in physics and quantum chemistry. Although most ground state properties of the UEG have been known for decades, a full thermodynamic description at WDM conditions has only been achieved recently [1,2]. In this contribution, we extend these considerations to the response of the UEG to an external perturbation, which is of key relevance both for theory and the interpretation of experiments.

More specifically, we have carried out extensive path integral Monte Carlo simulations of the UEG going from WDM conditions to the strongly correlated electron liquid regime to compute an imaginary-time density—density correlation function. The latter is subsequently used as input for a new reconstruction procedure, which allows to obtain ab initio results for the dynamic structure factor including all exchange-correlation effects [3,4]. Interestingly, we find nontrivial shapes around intermediate wave vectors, which manifest in a negative dispersion relation at strong coupling.

Moreover, we present extensive new results and a subsequent machine-learning representation of the static local field correction [5], which is of high importance for many applications, and new results for the electron liquid regime [6].

[1] S. Groth et al., Phys. Rev. Lett. 119, 135001 (2017)
[2] T. Dornheim et al., Phys. Reports 744, 1-86 (2018)
[3] T. Dornheim et al., Phys. Rev. Lett. 121, 255001 (2018)
[4] S. Groth et al., Phys. Rev. B 99, 235122 (2019)
[5] T. Dornheim et al., J. Chem. Phys. 151, 194104 (2019)
[6] T. Dornheim et al., Phys. Rev. B 101, 045129 (2020)