Superconductor-insulator transition in fccGeSb2Te4at elevated pressures

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 -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.

Memory of pressure-induced superconductivity in a phase-change alloy

“…By applying pressure, the different initial phases of GST experience sequential structural evolutions, which all end up in close-packed bcc structures with similar high density, but varying features depending on the initial composition. It has been proposed that disorder in the amorphous and vacancy-rich metastable cubic structure of GST can be additionally modulated leading to a delocalization of the electrons and hence initiating the insulator-metal or even insulator-superconductor transitions [11,12,32,33]. However, we found the novel pressure-induced phase transitions routine: trigonal-amorphous-bcc, the difference is likely due to difference in the microstructure of the initial trigonal phase.…”

“…In this work, we report the discovery of superconductivity in Ge 2 Sb 2 Te 5 with structure transformations from the starting trigonal phase in the compression and decompression process. Taking into account the high-pressure behaviors of GeSb 2 Te 4 [32,33], we further demonstrate the general nature of the emergent superconductivity in high-pressure phases of GST. The trigonal Ge 2 Sb 2 Te 5 characterized as a structure with randomly occupied Ge/Sb layers at ambient goes from the trigonal phase to amorphous and then to the body-centered cubic one with pressure.…”

The Structure of Phase‐Change Chalcogenides and Their High‐Pressure Behavior

“…Pressure is another basic thermodynamic parameter that is independent of, yet closely related to temperature, and therefore it can also affect phase stability and properties of materials . For instance, pressure‐induced superconductivity is observed in GeSb 2 Te 4 polycrystal where superconducting critical temperature ascends with pressure Phase‐change switching of PCMs often occurs on time scale of nanoseconds or even several hundred picoseconds, indicating that atoms do not require long‐distance diffusion in such a short period of time.…”

Multiple phase transitions in Sc doped Sb2Te3 amorphous nanocomposites under high pressure

“…This behavior is in accordance with the pressure-induced phase change in amorphous GST. 6,7 Finally, upon decompression, the resistance returns to the initial value. This distinct physical property originated from different bonding mechanisms in amorphous and crystalline phases.…”

“…Realizing improved trade-off between crystallization speed (writing) and amorphous phase stability (data retention) remains a challenging issue in PCM. Over the past few decades, amorphous Ge 2 Sb 2 Te 5 and Ge 1 Sb 2 Te 4 (both referred to as GST in this Letter) have received much attention as the matured PCMs, [2][3][4][5][6][7] but are still limited by the tens of nanoseconds writing speed due to the stochastic crystal nucleation during crystallization. Prototypical amorphous Sb 2 Te 3 shows a more rapid crystallization rate than GST at high temperature but has poor thermal stability at room temperature.…”