Warm dense matter created by isochoric laser heating

Warm Dense Matter (WDM) physics has been a growing field of high energy density physics, driven by the fundamental urge to understand the convergence between plasma and condensed matter physics, and the practical need to understand dynamic behavior of materials under extreme conditions. A platform for creating and probing WDM by isochoric heating of free-standing nano-foils has been developed recently to study the non-equilibrium processes. Results of optical measurements reveal the existence of a quasi-steady state in the time history, during which the interband component of the dielectric function shows both enhancement and a red shift. First-principles calculations of the dielectric function suggest that the enhanced red shift of the interband transition peak might be explained by a positive charge state of the gold foil due to ejection of electrons by the high intensity laser pulse. The impact on optical properties by the formation of an electronic sheath was examined by the Thomas–Fermi theory with local equilibrium approximation.