Longitudinal acoustic and higher-energy excitations in the liquid phase-change material Ge2Sb2Te5

M. Inui, Y. Kajihara, S. Hosokawa, A. Chiba, Y. Nakajima, K. Matsuda, Y. Tsuchiya, J. R. Stellhorn, T. Hagiya, H. Uchiyama, S. Tsutsui, A. Q.R. Baron

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1 Citation (Scopus)

Abstract

The dynamic structure factor S(Q,E) of liquid Ge2Sb2Te5 has been obtained by inelastic x-ray scattering, where Q and E are momentum and energy transfer, respectively. The dispersion curve of the longitudinal acoustic excitation energy exhibits flat-topped Q dependence similarly to that in liquid GeTe and liquid Bi, where the local structure is modulated by Peierls distortion. The flat-topped energy in liquid Ge2Sb2Te5 is split into low and high energy parts arising from Sb-Te and Ge-Te correlations, respectively. Furthermore, the high energy part depends on Q like an optical mode with decreasing Q to zero, and it approaches the vibrational energy of fourfold coordinated Ge atoms with octahedral configurations. The result indicates that a majority of Ge in the liquid stays in octahedral order as predicted by first-principles molecular dynamics simulations.

Original languageEnglish
Article number064202
JournalPhysical Review B
Volume104
Issue number6
DOIs
Publication statusPublished - 2021 Aug 1

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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