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.
@article{arxiv.1510.01857,
title = {Quantum criticality in AFe2As2 with A = K, Rb, and Cs suppresses superconductivity},
author = {Felix Eilers and Kai Grube and Diego A. Zocco and Thomas Wolf and Michael Merz and Peter Schweiss and Rolf Heid and Robert Eder and Rong Yu and Jian-Xin Zhu and Qimiao Si and Takasada Shibauchi and Hilbert v. Löhneysen},
journal= {arXiv preprint arXiv:1510.01857},
year = {2016}
}