Insulator-to-conducting transition in dense fluid helium.
By combining diamond-anvil-cell and laser-driven shock wave techniques, we produced dense He samples up to 1.5 g/cm(3) at temperatures reaching 60 kK. Optical measurements of reflectivity and temperature show that electronic conduction in He at these conditions is temperature-activated (semiconducting). A fit to the data suggests that the mobility gap closes with increasing density, and that hot dense He becomes metallic above approximately 1.9 g/cm(3). These data provide a benchmark to test models that describe He ionization at conditions found in astrophysical objects, such as cold white dwarf atmospheres.
Celliers
P M
PM
Lawrence Livermore National Laboratory, Post Office Box 808, Livermore, California 94551, USA.
Loubeyre
P
P
Eggert
J H
JH
Brygoo
S
S
McWilliams
R S
RS
Hicks
D G
DG
Boehly
T R
TR
Jeanloz
R
R
Collins
G W
GW