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

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.