Photoexcited GeTe undergoes a nonthermal phase transition from a rhombohedral to a rocksalt crystalline phase. The microscopic mechanism and the nature of the transition are unclear. By using constrained density functional perturbation theory and by accounting for quantum anharmonicity within the stochastic self-consistent harmonic approximation, we show that the nonthermal phase transition is strongly first order and does not involve phonon softening, at odds with the thermal one. The transition is driven by the closure of the single particle gap in the photoexcited rhombohedral phase. Finally, we show that ultrafast x-ray diffraction data are consistent with a coexistence of the two phases, as expected in a first order transition. Our results are relevant for the understanding of phase transitions and bonding in phase change materials.

First-Order Rhombohedral-to-Cubic Phase Transition in Photoexcited GeTe / Furci, Matteo; Marini, Giovanni; Calandra, Matteo. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 132:23(2024), p. 236101. [10.1103/physrevlett.132.236101]

First-Order Rhombohedral-to-Cubic Phase Transition in Photoexcited GeTe

Furci, Matteo
Primo
;
Marini, Giovanni
Secondo
;
Calandra, Matteo
Ultimo
2024-01-01

Abstract

Photoexcited GeTe undergoes a nonthermal phase transition from a rhombohedral to a rocksalt crystalline phase. The microscopic mechanism and the nature of the transition are unclear. By using constrained density functional perturbation theory and by accounting for quantum anharmonicity within the stochastic self-consistent harmonic approximation, we show that the nonthermal phase transition is strongly first order and does not involve phonon softening, at odds with the thermal one. The transition is driven by the closure of the single particle gap in the photoexcited rhombohedral phase. Finally, we show that ultrafast x-ray diffraction data are consistent with a coexistence of the two phases, as expected in a first order transition. Our results are relevant for the understanding of phase transitions and bonding in phase change materials.
2024
23
Furci, Matteo; Marini, Giovanni; Calandra, Matteo
First-Order Rhombohedral-to-Cubic Phase Transition in Photoexcited GeTe / Furci, Matteo; Marini, Giovanni; Calandra, Matteo. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 132:23(2024), p. 236101. [10.1103/physrevlett.132.236101]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/412230
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