Study of The Boson Peak in Phase-Change Materials using Machine-Learning Potential Simulations

Abstract

The boson peak is a peculiar feature in the vibrational density of states, mostly observed in disordered materials. Its origin has been attributed to various factors such as defects, atomic disorder, or mass density fluctuations [1,2], while a consensus is not reached yet. We investigate the boson peak in amorphous and metastable cubic Ge-Sb-Te phase-change materials to determine primary driving mechanism behind the boson peak. Utilizing the Gaussian approximation potentials [3] and a machine-learning scheme named the randomized atomic-system generator [4], we conduct large-scale simulations inaccessible from first-principles calculations to investigate this phenomenon. We employ an analytical approach involving the elastic theory, Voronoi cell analysis, atomic scale stress and strain to demonstrate the correlation between atomic disorder, density variation, shear elastic heterogeneity and the boson peak in the phase change materials.<br/><br/>References<br/>1. Hu, Y.-C. & Tanaka, H. Nat. Phys. 18, 669–677 (2022).<br/>2. Chumakov, A. I. et al. Phys. Rev. Lett. 112, 025502 (2014).<br/>3. Bartók, A. P., Payne, M. C., Kondor, R. & Csányi, G. Phys. Rev. Lett. 104, 136403 (2010).<br/>4. Choi, Y.-J. & Jhi, S.-H. J. Phys. Chem. B 124, 8704–8710 (2020).