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Ultrafast strain propagation and acoustic resonances in nanoscale bilayer systems

Ultrafast structural probing has greatly enhanced our understanding of the coupling of atomic motion to electronic and phononic degrees-of-freedom in quasi-bulk materials. In bi- and multilayer model systems, additionally, spatially inhomogeneous relaxation channels are accessible, often governed by...

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Autores principales: Bach, N., Schäfer, S.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Crystallographic Association 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8214470/
https://www.ncbi.nlm.nih.gov/pubmed/34169119
http://dx.doi.org/10.1063/4.0000079
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author Bach, N.
Schäfer, S.
author_facet Bach, N.
Schäfer, S.
author_sort Bach, N.
collection PubMed
description Ultrafast structural probing has greatly enhanced our understanding of the coupling of atomic motion to electronic and phononic degrees-of-freedom in quasi-bulk materials. In bi- and multilayer model systems, additionally, spatially inhomogeneous relaxation channels are accessible, often governed by pronounced interfacial couplings and local excitations in confined geometries. Here, we systematically explore the key dependencies of the low-frequency acoustic phonon spectrum in an elastically mismatched metal/semiconductor bilayer system optically excited by femtosecond laser pulses. We track the spatiotemporal strain wave propagation in the heterostructure employing a discrete numerical linear chain simulation and access acoustic wave reflections and interfacial couplings with a phonon mode description based on a continuum mechanics model. Due to the interplay of elastic properties and mass densities of the two materials, acoustic resonance frequencies of the heterostructure significantly differ from breathing modes in monolayer films. For large acoustic mismatch, the spatial localization of phonon eigenmodes is derived from analytical approximations and can be interpreted as harmonic oscillations in decoupled mechanical resonators.
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spelling pubmed-82144702021-06-23 Ultrafast strain propagation and acoustic resonances in nanoscale bilayer systems Bach, N. Schäfer, S. Struct Dyn ARTICLES Ultrafast structural probing has greatly enhanced our understanding of the coupling of atomic motion to electronic and phononic degrees-of-freedom in quasi-bulk materials. In bi- and multilayer model systems, additionally, spatially inhomogeneous relaxation channels are accessible, often governed by pronounced interfacial couplings and local excitations in confined geometries. Here, we systematically explore the key dependencies of the low-frequency acoustic phonon spectrum in an elastically mismatched metal/semiconductor bilayer system optically excited by femtosecond laser pulses. We track the spatiotemporal strain wave propagation in the heterostructure employing a discrete numerical linear chain simulation and access acoustic wave reflections and interfacial couplings with a phonon mode description based on a continuum mechanics model. Due to the interplay of elastic properties and mass densities of the two materials, acoustic resonance frequencies of the heterostructure significantly differ from breathing modes in monolayer films. For large acoustic mismatch, the spatial localization of phonon eigenmodes is derived from analytical approximations and can be interpreted as harmonic oscillations in decoupled mechanical resonators. American Crystallographic Association 2021-06-18 /pmc/articles/PMC8214470/ /pubmed/34169119 http://dx.doi.org/10.1063/4.0000079 Text en © 2021 Author(s). https://creativecommons.org/licenses/by/4.0/All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) ).
spellingShingle ARTICLES
Bach, N.
Schäfer, S.
Ultrafast strain propagation and acoustic resonances in nanoscale bilayer systems
title Ultrafast strain propagation and acoustic resonances in nanoscale bilayer systems
title_full Ultrafast strain propagation and acoustic resonances in nanoscale bilayer systems
title_fullStr Ultrafast strain propagation and acoustic resonances in nanoscale bilayer systems
title_full_unstemmed Ultrafast strain propagation and acoustic resonances in nanoscale bilayer systems
title_short Ultrafast strain propagation and acoustic resonances in nanoscale bilayer systems
title_sort ultrafast strain propagation and acoustic resonances in nanoscale bilayer systems
topic ARTICLES
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8214470/
https://www.ncbi.nlm.nih.gov/pubmed/34169119
http://dx.doi.org/10.1063/4.0000079
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