Density Functional and Non-Equilibrium Methods for Unusual States of Matter Produced Using Short-Pulse Lasers

Abstract

Density functional theory (DFT)^1–3 has proved itself as a very effective first principles calculational method for describing the electronic and structural properties of atoms, solids, liquids and plasmas. DFT is, of course, a method for equilibrium ensembles. However, using the output of DFT calculations as the input to non-equilibrium field-theory techniques, we obtain an extremely versatile theoretical framework which is not just a formal method, but an effective calculational method for confronting experimental results via first principles calculations. Just such a versatile and powerful tool is needed to understand the new states of matter that are being produced by the use of short-pulse lasers to compress, heat, ionize and manipulate matter into very unusual non-equilibrium situations. Such non-equilibrium situations are experimentally monitored using time-resolved probes which provide information on time dependent populations, optical and carrier transport coefficients, linear and non-linear susceptibilities, etc. It is clear from the talks by Profs. Mike Downer, Tom Hall, and von der Linde, that the time evolution of such systems during energy deposition by the laser may involve the transformation of the solid to other solid phases, to a liquid and finally to a plasma. Hence the first principles method must have the capability of spanning such a variety of regimes of condensed matter.