High-pressure superconducting phase diagram of⁶Li: Isotope effects in dense lithium

Abstract

Significance The emergence of exotic quantum states, such as fluid ground state and two-component superconductivity and superfluidity, in a compressed light metallic system has been entertained theoretically for metallic phases of hydrogen. The difficulty of compressing hydrogen to metallization densities has prevented experimental proof of these effects. Studying lithium, which is isovalent to hydrogen and the lightest metal, is considered as a route to studying the lattice quantum effects in a dense light metallic system. Here, by comparing the superconductivity of lithium isotopes under pressure, we present evidence that properties of lithium at low temperature may significantly be dominated by its lattice quantum dynamics. This study is the first experimental report on superconducting properties of 6 Li, the lightest superconducting material.