Warm Dense Matter: The missing link between condensed matter and plasma

Summary form only given. Although most laboratory plasmas are produced from heating of solids, little is known about the properties of the intervening states during evolution of a cold solid into hot plasma. Such states lie in the so-called Warm Dense Matter regime where temperature is comparable to Fermi energy and density is sufficiently high to render the ions strongly coupled. Experimental studies of Warm Dense Matter are challenging due to extreme pressure (~Mbar) of the states while theoretical studies are greatly complicated by the interplay of electronic excitation, electron degeneracy, and strong ion-ion correlation effects. Nonetheless, since its emergence in 1999 Warm Dense Matter has been rapidly gathering interest. This is driven by the fundamental significance of understanding the convergence of condensed matter and plasma physics as well as the relevance of Warm Dense Matter to broad areas including material science under extreme conditions, inertial confinement fusion, and planetary physics. Advances in Warm Dense Matter research are being propelled simultaneously by (i) ready availability of intense energy sources including lasers, free electron lasers, X-rays and energetic particles (electron and ion), and (ii) increasing capability in ab-initio molecular dynamic simulations. In this talk I will begin with a brief introduction to Warm Dense Matter. This will be followed by discussions on our earlier studies of electron-ion coupling, AC conductivity and solid-plasma transition in Warm Dense Matter states with energy density of ~10¹¹J/m³.