Dresden 2003 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

PV: Plenarvorträge

PV IX

PV IX: Plenarvortrag

Donnerstag, 27. März 2003, 08:30–09:15, HSZ/01

Ordered quantum liquid states in dense Hydrogen and Deuterium — •Neil W. Ashcroft — Laboratory of Atomic and Solid State Physics, Cornell University, Ithaka NY 14853, USA

We normally associate the fluid states of metals with phases where the ionic or nuclear degrees of freedom may be viewed in classical terms while the valence electrons continue to be significantly quantal, remaining close to degenerate. The question to be addressed is whether there may be systems accessible in the laboratory, where the metallic state is a translationally invariant fluid, but where for appropriate thermodynamic conditions (especially low temperatures) the nuclei are also fully quantal. It is evident that zero-point energies must play a central role in raising such a possibility and the most favorble cases will therefore involve systems with the lowest masses, especially the hydrogens (protium, deuterium and even tritium). Experiments and simulations studies already suggest that hydrogen under compression may posses a melting point maximum, and it has therefore been suggested that the succeeding decline in the melting curve may extend to regions of density where a low temperature liquid phase is preferred over the solid and, inter alia, at densities sufficient to induce an insulator-metal transition. Calculations suggest that this may be expected around 13.5-fold compression, current static experiments on dense hydrogen already exceeding 12-fold compression. Questions then immediately arise about the physical characteristics of such low temperature fluid metallic states, including the nature of quantum ordered states for both electrons and nuclei. These will be shown to be strikingly different from classical liquid metals with quantum statistics of the nuclei (spin half protium, fermion; spin one deuterium, boson; and spin half tritium, fermion) playing an especially prominent role.

Work supported by the US National Science Foundation