Herzfeld instability versus Mott transition in metal-ammonia solutions

Abstract

Although most metal-insulator transitions in doped insulators are generally viewed as Mott transitions, some systems seem to deviate from this scenario. Alkali metal-ammonia solutions are a brilliant example of that. They reveal a phase separation in the range of metal concentrations where a metal-insulator transition occurs. Using a mean spherical approximation for quantum polarizable fluids, we argue that the origin of the metal-insulator transition in such a system is likely similar to that proposed by Herzfeld a long time ago, namely, due to fluctuations of solvated electrons. We also show how the phase separation may appear: the Herzfeld instability of the insulator occurs at a concentration for which the metallic phase is also unstable. As a consequence, the Mott transition cannot occur at low temperatures. The proposed scenario may provide a new insight into the metal-insulator transition in condensed-matter physics.

9 pages, 4 figures

Cited by in corpus (2)

• Nature of the metal-nonmetal transition in metal-ammonia solutions. I. Solvated electrons at low metal concentrations
• Nature of metal-nonmetal transition in metal-ammonia solutions. II. From uniform metallic state to inhomogeneous electronic microstructure