Superconductor-insulator transition in fcc-GeSb2Te4 at elevated pressures

TL;DR

This study demonstrates that fcc-GeSb2Te4 transitions from an insulator to a superconductor under high pressure, revealing a quantum phase transition and structural changes, with notable magnetoresistance anomalies.

Contribution

It uncovers the pressure-induced superconductor-insulator transition and structural phase changes in fcc-GeSb2Te4, including the emergence of superconductivity in different phases.

Findings

f-GST becomes superconducting at elevated pressures

Second order quantum phase transition with linear scaling of Tc

Anomalous magnetoresistance peak in mixed phase regime

Abstract

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.