THz elastic dynamics in finite-size CoFeB-MgO phononic superlattices

In this article, we present the observation of coherent elastic dynamics in a nano-scale phononic superlattice, which consists of only 4 bilayers. We demonstrate how ultra-short light pulses with a length of 40 fs can be utilized to excite a coherent elastic wave at 0.535 THz, which persist over abo...

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Bibliographic Details
Published in:Journal of applied physics 2016-10, Vol.120 (14)
Main Authors: Ulrichs, Henning, Meyer, Dennis, Müller, Markus, Wittrock, Steffen, Mansurova, Maria, Walowski, Jakob, Münzenberg, Markus
Format: Article
Language:English
Subjects:
Applied physics
Bilayers
CHANNELING
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Elastic waves
LAYERS
LENGTH
MAGNESIUM OXIDES
Periodic variations
PERIODICITY
PHONONS
PULSES
SUPERLATTICES
Wave physics
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Summary:In this article, we present the observation of coherent elastic dynamics in a nano-scale phononic superlattice, which consists of only 4 bilayers. We demonstrate how ultra-short light pulses with a length of 40 fs can be utilized to excite a coherent elastic wave at 0.535 THz, which persist over about 20 ps. In later steps of the elastic dynamics, modes with frequency of 1.7 THz and above appear. All these modes are related to acoustic band gaps. Thus, the periodicity strongly manifests in the wave physics, although the system under investigation has only a small number of spatial periods. To further illustrate this, we show how by breaking the translational invariance of the superlattice, these features can be suppressed. Discussed in terms of phonon blocking and radiation, we elucidate in how far our structures can be considered as useful building blocks for phononic devices.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4961978