Static Density Response of the Warm Dense Electron Gas beyond Linear Response Theory: Excitation of Harmonics.
ORAL
Abstract
Experimental setups as well as theoretical modeling of Warm Dense Matter (WDM) heavily rely on linear response theory. However, Dornheim et. al. [Phys. Rev. Lett.125, 085001 (2020)] showed that assuming the linear regime is not always justified for WDM. We use the ab initio Path-Integral Monte-Carlo (PIMC) technique to obtain exact results for the harmonically perturbed homogeneous electron gas. A thorough analysis for different perturbation amplitudes is carried out. The corresponding density response reveals resonances at higher harmonics of the perturbation frequency. Furthermore, the induced density response as a function of the perturbation strength unveils that the dominant term beyond linear response is the second harmonic. We show that the nonlinear density response is highly sensitive to exchange–correlation effects, rendering it a potentially valuable new diagnostic tool. The results signify the importance of response contributions beyond the linear regime to accurately model WDM.
*This work was partly funded by the Center for Advanced Systems Understanding (CASUS) which is financed by Germany's Federal Ministry of Education and Research (BMBF) and by the Saxon Ministry for Science, Culture and Tourism (SMWK) with tax funds on the basis of the budget approved by the Saxon State Parliament, and by the Deutsche Forschungsgemeinschaft (DFG) via project BO1366/15.The PIMC calculations were carried out at the Norddeutscher Verbund für Hoch- und Höchstleistungsrechnen (HLRN) under grant shp00026, on a Bull Cluster at the Center for Information Services and High Performace Computing (ZIH) at Technische Universität Dresden, on the cluster hemera at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), and at the computing center (Rechenzentrum) of Kiel university.
