Quantum criticality in AFe2As2 with A = K, Rb, and Cs suppresses superconductivity

TL;DR

This study investigates how increasing alkali-metal ion size in AFe2As2 superconductors approaches a quantum critical point, revealing that critical fluctuations near this point suppress superconductivity.

Contribution

It provides the first detailed analysis of band-specific quasiparticle masses and their pressure dependence in AFe2As2 with A = K, Rb, Cs, linking electronic correlations to quantum criticality.

Findings

Quantum critical point is approached with larger alkali-metal ions.

Critical fluctuations suppress superconductivity near the quantum critical point.

Electronic correlations increase as the system approaches the critical point.

Abstract

Superconductors close to quantum phase transitions often exhibit a simultaneous increase of electronic correlations and superconducting transition temperatures. Typical examples are given by the recently discovered iron-based superconductors. We investigated the band-specific quasiparticle masses of AFe2As2 single crystals with A = K, Rb, and Cs and determined their pressure dependence. The evolution of electronic correlations could be tracked as a function of volume and hole doping. The results indicate that with increasing alkali-metal ion radius a quantum critical point is approached. The critical fluctuations responsible for the enhancement of the quasiparticle masses appear to suppress the superconductivity.