期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：1
页码：60-64
DOI：10.1073/pnas.1412638112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceThe 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 6Li, the lightest superconducting material. We measured the superconducting transition temperature of 6Li between 16 and 26 GPa, and report the lightest system to exhibit superconductivity to date. The superconducting phase diagram of 6Li is compared with that of 7Li through simultaneous measurement in a diamond anvil cell (DAC). Below 21 GPa, Li exhibits a direct (the superconducting coefficient, , [IMG]f1.gif" ALT="Formula" BORDER="0"> is positive), but unusually large isotope effect, whereas between 21 and 26 GPa, lithium shows an inverse superconducting isotope effect. The unusual dependence of the superconducting phase diagram of lithium on its atomic mass opens up the question of whether the lattice quantum dynamic effects dominate the low-temperature properties of dense lithium.
