AC conductivity and electron transport studies in non-equilibrium warm dense gold

Summary form only given. We will present results of our studies on electron energy transport and AC conductivity in non-equilibrium warm dense gold produced by femtosecond laser heating. The results are deduced from single short measurements of reflectivity and transmissivity using a chirped pulse probe technique. In our electron transport study, we observed an abrupt change in energy transport in femtosecond-laser heated gold when the absorbed laser flux exceeds 7xlO´2W/cm2 [1]. Below this value, the absorbed flux is carried by ballistic transport of non-thermal electrons produced in interband excitation. Above this value, energy transport appears to include both ballistic transport by non-thermal electrons and heat diffusion by thermalized hot electrons. The ballistic component appears to be limited to a flux of 7x10 12W/cm2 [2]. In our AC conductivity study, we measured the temporal evolution of AC conductivity during electron energy relaxation in non-equilibrium warm dense gold. The measurements provide the first benchmark for testing an abinitio model that is used to calculate electron heat capacity, electron-ion coupling and AC conductivity in a single, first principles framework. While measurements of the real part of AC conductivity corroborate our theoretical temperature dependent electron heat capacity, they point to an electronion coupling factor substantially below that predicted by theory. In addition, measurements of the imaginary part of AC conductivity reveal the need to improve theoretical treatment of intraband contribution at very low photon energy [2].