Strong field physics close to or above the Schwinger limit are typically studied with the vacuum as initial condition [1, 2], or by considering test particle dynamics. However, with a plasma present
initially, quantum relativistic mechanisms such as Schwinger pair-creation are complemented by classical plasma nonlinearities.

In this work we use the Dirac-Heisenberg-Wigner formalism [3] to study the interplay between classical and quantum mechanical mechanisms for ultra-strong electric fields. In particular, the effects of initial density and temperature on the plasma oscillation dynamics are determined. In comparison with previous works [4], the physical value of the fine structure constant has been used.