Physics beyond homogeneous warm dense matter

Warm dense matter (WDM) is a state of matter covering parameter space between solids and dense plasmas, and is characterized by the simultaneous relevance of electronic quantum degeneracy, thermal excitations, and strong inter-particle correlations. WDM is an interdisciplinary field between plasma physics, condensed matter physics, high pressure science, inertial confinement fusion, planetary science, and materials science under extreme conditions [1-3]. Therefore, WDM is a complex regime to which neither ordinary condensed matter theory nor plasma theory are applicable. In particular, a highly ionized WDM state is closely related to a non-ideal dense plasma state. Parameters of relevant WDM experiments are shown in Fig.1 along with other types of plasma states. Due to relatively well developed theoretical and computational methods for homogeneous states, most of the initial studies were focused on uniform WDM. However, recent introduction of THz lasers [4], the novel seeding technique to reach high intensities [5], and laser pumping of a sample with a pre-designed periodic grating structure [6] allows us to generate inhomogeneous states. Therefore, this talk will be focused on inhomogeneous states.
In particular, periodically inhomogeneous WDM is considered. The results will be presented for collective oscillations in such systems. It will be shown that such interesting features like double plasmon and optical mode appear in electronic density excitation spectra. Additionally, the non-linear density response of electrons and applicability of various exchange-correlation functionals such as LDA, GGA, and meta-GGA will be discussed. The analysis of the quality of the KS-DFT approach based on different exchange-correlations functionals is performed by comparing to QMC data. Finally, the quantum fluid theory of inhomogeneous quantum electrons will be presented. The results on the first ab inito study of the many-fermion Bohm field will be shown. The latter has impact going well beyond WDM, since it is key quantity of Bohmenian quantum mechanics.

[1] A. Ng, IEEE International Conference on Plasma Science (Cat. No.02CH37340),
2002, pp. 163-, doi: 10.1109/PLASMA.2002.1030367.
[2] F. Graziani, M. P. Desjarlais, R. Redmer, and S. B. Trickey, Frontiers and Chal-
lenges in Warm Dense Matter (Springer, 2014).
[3] V. E. Fortov,Extreme States of Matter (Springer, Heidelberg, 2016).
[4] B.K. Ofori-Okai, et al., J. Inst13, P06014 (2018).
[5] T Kluge, et al., Phys. Rev. X 8, 031068 (2018).