Dense Hydrogen at High and Low Temperatures

Abstract

Hydrogen, at near 9-fold compression and at low temperatures, conforms to a time-averaged state of crystalline symmetry. By shock methods it can be transiently taken into a state of continuous symmetry which, at approximately the same compression, is at a temperature equivalent to about 0.27 eV. Here it is reported to be significantly conducting, and an appraisal of this state via band-theory suggests that it is not inconsistent either with the electronic character typical of a significantly excited narrow gap semiconductor or, with less certainty, a band-overlap semimetallic state. These states develop from low temperature phases representable by a Landau theory formulated in terms of the order associated with three principal domains, one a crystalline but rotational state, the second a crystalline but highly librating phase, and the third a self-sustaining crystalline assembly of dipoles augmented with significant dynamic polarization.

Work supported by the National Science Foundation.