The Impact of Long-Wavelength Collective Motion on the Electron Distribution Function and Transport in Warm Dense Plasmas

Recent shock-compression experiments of liquid deuterium [1,2] show that all wide-range theoretical equation-of-state (EOS) models underestimate the compressibility of warm dense deuterium (where thermal energy, Coulomb energy, and Fermi energy are all comparable), suggesting an underestimation of the internal energy of deuterium. The collective motion in plasmas [3], like phonons in solids, contribute to a material’s EOS and transport properties, but the long wavelengths of these modes are challenging to simulate with today’s finite-size quantum simulation techniques [4,5] due to limited computational resources. A simple Debye-type calculation of the energy of electron plasma waves (EPWs) has been shown to account for the missing piece of internal energy [6]. In this work, we investigate how these EPW excitations modify the electron energy distribution function—a critical input to quantum simulation methods and other theoretical models. We estimate the impact of the modified distribution function on transport properties such as thermal conductivity and opacity. This work highlights the importance of properly handling long-wavelength collective motion in warm dense plasma modeling.

[1] D. E. Fratanduono et al., Phys. Plasmas 26, 012710 (2019).

[2] A. Fernandez-Pañella et al., Phys. Rev. Lett. 122, 255702 (2019).

[3] D. Bohm and D. Pines, Phys. Rev. 92, 609 (1953).

[4] T. Dornheim, S. Groth, and M. Bonitz, Phys. Rep. 744, 1 (2018).

[5] T. Dornheim et al., Phys. Rev. B 103, 205142 (2021).

[6] J. R. Rygg, P. M. Celliers, and G. W. Collins, Phys. Rev. Lett. 130, 225101 (2023).