Spontaneously formed phonon frequency combs in van der Waals solid CrXTe\(_3\) (X=Ge,Si)

Optical phonon engineering through nonlinear effects has been utilized in ultrafast control of material properties. However, nonlinear optical phonons typically exhibit rapid decay due to strong mode-mode couplings, limiting their effectiveness in temperature or frequency sensitive applications. In...

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Bibliographic Details
Published in:arXiv.org 2024-11
Main Authors: Chen, Lebing, Ye, Gaihua, Nnokwe, Cynthia, Xing-Chen, Pan, Tanigaki, Katsumi, Cheng, Guanghui, Chen, Yong P, Jiaqiang Yan, Mandrus, David G, Andres E Llacsahuanga Allcca, Giles-Donovan, Nathan, Birgeneau, Robert J, He, Rui
Format: Article
Language:English
Subjects:
Couplings
Germanium
Harmonic oscillators
Hexagons
Material properties
Nonlinear control
Nonlinear optics
Optical properties
Oscillations
Phonons
Raman spectra
Silicon
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Summary:Optical phonon engineering through nonlinear effects has been utilized in ultrafast control of material properties. However, nonlinear optical phonons typically exhibit rapid decay due to strong mode-mode couplings, limiting their effectiveness in temperature or frequency sensitive applications. In this study, we report the observation of long-lived nonlinear optical phonons through the spontaneous formation of phonon frequency combs in the van der Waals material CrXTe\(_3\) (X=Ge, Si) using high-resolution Raman scattering. Unlike conventional optical phonons, the highest \(A_g\) mode in CrGeTe\(_3\) splits into equidistant, sharp peaks forming a frequency comb that persists for hundreds of oscillations and survives up to 100K before decaying. These modes correspond to localized oscillations of Ge\(_2\)Te\(_6\) clusters, isolated from Cr hexagons, behaving as independent quantum oscillators. Introducing a cubic nonlinear term to the harmonic oscillator model, we simulate the phonon time evolution and successfully replicate the observed comb structure. Similar frequency comb behavior is observed in CrSiTe\(_3\), demonstrating the generalizability of this phenomenon. Our findings reveal that Raman scattering effectively probes high-frequency nonlinear phonon modes, providing new insight into generating long-lived, tunable phonon frequency combs with applications in ultrafast material control and phonon-based technologies.
ISSN:2331-8422