Charge and energy confinement of strongly coupled plasma within a phase-coexisting supercritical fluid

Strongly coupled plasmas (SCPs) are believed to exist in various places in the universe. Neutron stars, white dwarf stars, and the cores of Jovian planets are some examples. Several theoretical models and numerical simulations have been developed in recent decades to describe the particle interactions in SCPs, which fundamentally differ from those in conventional weakly coupled plasmas. However, even the basic equation of states is yet to be verified by experiments. The main difficulty in SCP experiments is that very high energy should be confined both in space and time. We demonstrate a method to enhance the charge and energy confinement of strongly coupled plasmas produced by pulsed laser discharge by utilizing inhomogeneous supercritical fluids. We recently discovered that a single-component supercritical fluid, which is considered a homogeneous medium, can be prepared in a quasi-stable inhomogeneous state containing a dense population of nanometer-size liquid-like clusters and a small number of submicron-size droplets that survive for an hour [Nat. Commun., accepted]. In laser discharges of argon SCPs, it is observed that the clusters and droplets prolong the charge and energy relaxation time of the plasma up to about microseconds. This finding alleviates the problem of short timescales in strongly coupled plasma experiments and will allow measurements of plasma parameters for a more in-depth understanding of the charge and energy transport of strongly coupled plasma.