# Evidence for superconductivity in Rb metal above 55 GPa pressure

## TL;DR

This study confirms superconductivity in cesium under pressure and provides strong evidence that rubidium also becomes superconducting near 2 K at 55 GPa, suggesting many alkali metals can be superconductors under specific conditions.

## Contribution

The paper presents experimental confirmation of superconductivity in cesium and new evidence of rubidium's superconductivity at high pressure, expanding the known alkali metals with this property.

## Key findings

- Cesium becomes superconducting near 1.3 K at 12 GPa.
- Rubidium shows strong evidence of superconductivity near 2 K at 55 GPa.
- Superconductivity may be common among alkali metals under high pressure.

## Abstract

The only alkali metal known to be superconducting at ambient pressure is Li at 0.4 mK. Under 30 GPa pressure \textit{T}$_{c}$ for Li rises to 14 K. In addition, nearly 50 years ago the heavy alkali metal Cs was reported to become superconducting near 1.3 K at 12 GPa. In the present experiment the superconductivity of Cs under pressure is confirmed. In addition, strong evidence is presented in electrical resistivity measurements that neighboring Rb also becomes superconducting near 2 K at 55 GPa as it enters the \textit{oC}16 phase, as for Cs, where \textit{T}$_{c}$ decreases under the application of pressure. It would seem likely that under the right temperature/pressure conditions all alkali metals, including metallic hydrogen, will join the ranks of the superconducting elements. With the addition of Rb, 55 of the 92 naturally occurring elements are superconducting at ambient or high pressure.