Structural and electronic properties of expanding fluid metals

Abstract

It has been theoretically predicted that interacting electron gas suffers a negativecompressibility when the electron density is sufficiently reduced. Dielectric anomaly isanother expression of compressional instability in which the static dielectric function ofelectron gas changes sign from positive to negative. In a medium with a negativedielectric function, like charges can attract. Expanding fluid alkali metals arethe ideal system in which such instability of electron gas can be probed via thestructural response of ions. We have performed x-ray diffraction and small angle x-rayscattering measurements using synchrotron radiation for expanding fluid rubidiumand cesium. On the basis of the experimental results we discuss the existence ofcompressional instability and dielectric anomaly in three-dimensional electrongas.