Striking isotope effect on the metallization phase lines of liquid hydrogen and deuterium

Liquid atomic metallic hydrogen is the simplest, lightest, and most abundant of all liquid metals. The importance of nucleon motions or ion dynamics can be studied by comparing the metallization phase lines of the dissociative insulator-metal transitions of hydrogen and deuterium. We use static compression to study the optical properties of dense liquid metallic deuterium in the pressure region of 1.2-1.7 Mbars and measured temperatures up to similar to 3000 K. At the same pressure (density) for the two isotopes, the phase lines of this transition reveal a prominent isotopic shift of similar to 700 K. Our paper shows the importance of quantum nuclear effects in the metallization transition and conduction properties in dense hydrogen isotopes at conditions of giant planetary interiors and provides an invaluable benchmark for ab initio calculations.