Reemerging superconductivity at 48 K across quantum criticality in iron chalcogenides

TL;DR

This study reveals that iron chalcogenide superconductors can exhibit reemerging superconductivity with record-high Tc up to 48.7 K after initial suppression under pressure, linked to quantum criticality.

Contribution

It demonstrates the reemergence of high-temperature superconductivity in iron chalcogenides under pressure, associated with quantum criticality, surpassing previous Tc records.

Findings

Superconductivity reappears at higher Tc after initial suppression.

Maximum Tc reaches 48.7 K in K0.8Fe1.70Se2.

Reemergence linked to pressure-induced quantum criticality.

Abstract

Pressure plays an essential role in the induction1 and control2,3 of superconductivity in iron-based superconductors. Substitution of a smaller rare-earth ion for the bigger one to simulate the pressure effects has surprisingly raised the superconducting transition temperature Tc to the record high 55 K in these materials4,5. However, Tc always goes down after passing through a maximum at some pressure and the superconductivity eventually tends to disappear at sufficiently high pressures1-3. Here we show that the superconductivity can reemerge with a much higher Tc after its destruction upon compression from the ambient-condition value of around 31 K in newly discovered iron chalcogenide superconductors. We find that in the second superconducting phase the maximum Tc is as high as 48.7 K for K0.8Fe1.70Se2 and 48 K for (Tl0.6Rb0.4)Fe1.67Se2, setting the new Tc record in chalcogenide superconductors. The presence of the second superconducting phase is proposed to be related to pressure-induced quantum criticality. Our findings point to the potential route to the further achievement of high-Tc superconductivity in iron-based and other superconductors.