We show that polycrystalline GeSb2Te4 in the fcc phase (f-GST), which is an insulator at low temperature at ambient pressure, becomes a superconductor at elevated pressures. Our study of the superconductor to insulator transition versus pressure at low temperatures reveals a second order quantum phase transition with linear scaling (critical exponent close to unity) of the transition temperature with the pressure above the critical zero-temperature pressure. In addition, we demonstrate that at higher pressures the f-GST goes through a structural phase transition via amorphization to bcc GST (b-GST), which also become superconducting. We also find that the pressure regime where an inhomogeneous mixture of amorphous and b-GST exists, there is an anomalous peak in magnetoresistance, and suggest an explanation for this anomaly.
@article{arxiv.1709.01844,
title = {Superconductor-insulator transition in fcc-GeSb2Te4 at elevated pressures},
author = {Bar Hen and Samar Layek and Moshe Goldstein and Victor Shelukhin and Mark Shulman and Michael Karpovski and Eran Greenberg and Eran Sterer and Yoram Dagan and Gregory Kh. Rozenberg and Alexander Palevski},
journal= {arXiv preprint arXiv:1709.01844},
year = {2018}
}