Energy Band Structure of Relativistic Quantum Plasmon Excitation

Abstract: In this paper we use the effective Schr\"{o}dinger-Poisson and square-root Klein-Gordon-Poisson models to study the quantum and relativistic quantum energy band structure of finite temperature electron gas in a neutralizing charge background. Based the plasmon band gap appearing above the Fermi level, new definitions on plasmonic excitations and plasma parameters in a wide electron temperature-density regime is suggested. The new equation of state (EoS) for excited electrons to the plasmon band leads to novel aspects of relativistic collective quantum excitations such as the plasmon black-out and quantum pressure collapse which are studied using both non-relativistic and relativistic quantum models. The plasmon black-out effect may be used to explain why metallic elements do not show collective behavior at low temperatures. The model can be used to predict phases of matter in which the plasmonic activities is shut down, hence, it may behave like a mysterious dark matter. On the other hand, the energy band structure model predicts the plasmon pressure collapse in temperature-density coordinates matching that of a white dwarf star. The prediction of energy band structure of collective quantum excitations may have direct implications for the inertial confinement fusion (ICF), the EoS of warm dense matter (WDM) and evolution of stellar and other unknown cosmological structures. It is found that predictions of non-relativistic and relativistic quantum excitation models closely match up to temperature-density of degenerate stars which confirms the relevance of non-relativistic plasmon models used in the warm and dense matter regime. The effect of positron on band structure of collective quantum excitations is also studied.