Temperature-driven topological quantum phase transitions in a phase-change material Ge2Sb2Te5

Abstract

The Ge2Sb2Te5 is a phase-change material widely used in optical memory devices and is a leading candidate for next generation non-volatile random access memory devices which are key elements of various electronics and portable systems. Despite the compound is under intense investigation its electronic structure is currently not fully understood. The present work sheds new light on the electronic structure of the Ge2Sb2Te5 crystalline phases. We demonstrate by predicting from first-principles calculations that stable crystal structures of Ge2Sb2Te5 possess different topological quantum phases: a topological insulator phase is realized in low-temperature structure and Weyl semimetal phase is a characteristic of the high-temperature structure. Since the structural phase transitions are caused by the temperature the switching between different topologically non-trivial phases can be driven by variation of the temperature. The obtained results reveal the rich physics of the Ge2Sb2Te5 compound and open previously unexplored possibility for spintronics applications of this material, substantially expanding its application potential.

Topological Phase Buried in a Chalcogenide Superlattice Monitored by Helicity-Dependent Kerr Measurement

“…However, the real structure of the iPCM may be more complicated than the model GeTe/Sb 2 Te 3 SL structure as intermixing of the layers has been reported. 46 Even though intermixing may occur, because the resultant ternary compounds still possess topological insulating properties, 47 it is expected that the large L value can be attributed to the topological properties of the GeTe/Sb 2 Te 3 SL, although more experimental and theoretical works will be required to fully understand the topological properties.…”

Topological phases in a Weyl semimetal multilayer

“…The vertex of the Dirac-cone dispersion is called a Weyl node, and it can be regarded as a monopole or an anti-monopole for the Berry curvature field in the wavevector space 4,6,7 . Various WSMs are predicted after these works, and as candidates of WSMs, pyrochlore iridates 5,8,9 , HgCr 2 Se 4 10,11 , TaAs 12 , Co 2 TiX (X=Si,Ge,Sn) 13 , ZrCo 2 Sn 14 , Mo x W 1−x Te 2 15 , Ge 2 Sb 2 Te 5 16 , TlBiSe 2 17 , Hg 1−x−y Cd x Mn y Te 18 in a magnetic field, and Bi 0.97 Sb 0.03 in a magnetic field 19 have been proposed. In recent years, some WSMs has been experimentally observed, such as TaAs [20][21][22][23][24] and NbAs 25 .…”

GeTe2 Phase Change Material for Terahertz Devices with Reconfigurable Functionalities Using Optical Activation

“…In the past years, with the intensive development of THz technologies, artificial materials got a new perspective, which was determined by the impact of conductivity on dielectric properties of matter in this frequency range, providing an opportunity to change the THz photonic properties of such materials. ,,− This resulted in wide application of functional materials such as doped semiconductors, graphene, ,, ferroelectric, , and PCMs. ,,, A special role among these materials is played by PCMs with variable conductivity function in order to photonic properties of materials caused by changes in the chemical or crystal structure after the phase change transition. The phase change transition process can be initiated by temperature effects, − laser radiation, , or an electric field. , By varying the initiating impact, it is possible to form an area with particular optical parameters.…”