Anomalous static electronic screening in compressed lithium

Lithium has long been considered a simple metal. However, under pressure lithium departs radically from this simple behavior, as it strongly enhances its superconducting transition temperature before phase transitions to complex structures emerge. Interestingly, these features are not unique of lithium, as have been also observed in other simple elements, but lithium becomes a good system to characterize their physical origin. In this article we will analyze anomalies arising in the static electronic susceptibility of lithium under pressure, where clear connections between anisotropies in the Fermi surface, phonon instabilities, and enhanced electron-phonon coupling will be shown.