Superconducting phase diagram of Li Metal in nearly hydrostatic pressures up to 67 GPa

TL;DR

This study maps the superconducting transition temperature of lithium under nearly hydrostatic pressures up to 67 GPa, revealing pressure-induced phase transitions and the nature of its superconductivity.

Contribution

It provides the first detailed pressure-dependent superconducting phase diagram of lithium using nearly hydrostatic conditions, highlighting competition with structural phase transitions.

Findings

Superconductivity appears at 5.47 K near 20 GPa.

T_{c} increases rapidly to ~14 K at 30 GPa.

Li is identified as a type I superconductor in this pressure range.

Abstract

The dependence of the superconducting transition temperature T_{c} on nearly hydrostatic pressure has been determined to 67 GPa in an ac susceptibility measurement for a Li sample embedded in helium pressure medium. With increasing pressure, superconductivity appears at 5.47 K for 20.3 GPa, T_{c} rising rapidly to ~ 14 K at 30 GPa. The T_{c}(P)-dependence to 67 GPa differs significantly from that observed in previous studies where no pressure medium was used. Evidence is given that superconductivity in Li competes with symmetry breaking structural phase transitions which occur near 20, 30, and 62 GPa. In the pressure range 20-30 GPa, T_{c} is found to decrease rapidly in a dc magnetic field, the first evidence that Li is a type I superconductor.