ESPCI web site
Thursday April 10 at 2:00 pm (Paris time),
Room Holweck, building C, 1st floor, at LPEM in hybrid format
Quantum absorption in the supercritical state of SF6
Critical phenomena and out-of-equilibrium properties drive the physics of phase-transitions. One particularly important class of phase transitions is the passage between the liquid and gaseous phases. This transformation ends at a critical point reached at specific conditions of temperature and pressure. Critical opalescence occurs at this singularity. Discovered in 1823, it is known to be driven by diverging fluctuations in the refractive index and the density at the critical point. During the past two decades, boundaries between the gas- and liquid-like regimes have been theoretically proposed and experiments have emerged indicating that the supercritical fluid is not featureless. We recently studied the fast cooling of near-critical sulfur hexafluoride (SF6) leading to dark opalescence. We found that, against what has been assumed for over one century, the dark opalescence is not the consequence of simple light scattering of visible photons. Our spectroscopic measurements show the formation of quantum states that absorb light. Remarkably these quantum states only exist in the out-of-equilibrium combination of liquid and gaseous phases. Our results suggest that excitations characteristic of solid-state physics can form in the liquid-gas mixture. This effect emerges as an out-of-equilibrium pattern driven by quantum effects in a quintessentially classical context.
