Pressure-Driven Quantum Criticality in An Iron-Selenide Superconductor

TL;DR

This study reveals pressure-induced quantum criticality in an iron-selenide superconductor, showing suppression of superconductivity, a semiconductor-metal transition, and changes in electronic transport properties.

Contribution

It provides the first evidence of pressure-driven quantum criticality in iron-selenide superconductors, linking magnetic, electronic, and structural transitions.

Findings

Superconducting Tc decreases with pressure.

Resistance hump TH shifts with pressure.

Quantum critical point at 8.7 GPa where superconductivity vanishes.

Abstract

The discovery of superconductivity of about 30 K in iron selenides with very large magnetic moments simulates the examination of completing orders. Here we report a finding of pressure- induced suppression of the superconducting transition temperature Tc and enhancement of the temperature of the resistance hump TH through charge transfer between two iron sites with different occupancies. The activation energy for the electric transport of the high-temperature resistance is observed to go to zero at a critical pressure of 8.7 GPa, at which superconductivity tends to disappear and the semiconductor-to-metal transition takes place. Beyond the critical point, the resistance exhibits a metallic behavior over the whole temperature range studied. All these features indicate the existence of quantum criticality in iron-selenide superconductors.