High Quality Content by WIKIPEDIA articles! Warm dense matter, abbreviated WDM, is the non-equilibrium state of matter between a solid and a plasma. It can be defined as the state that is too dense to be described by weakly coupled plasma physics yet that is too energetic to be described by condensed matter physics. In this state, the potential energy of the interaction between electrons and nuclei and the kinetic energy of electrons are of roughly the same magnitude. WDM has a density of the same order as a solid and a temperature of a few tens of thousands of kelvins (or a few electronvolts in the units favored by practitioners).