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DOE OSTI · 2572177

Spontaneously formed phonon frequency combs in van der Waals solid CrGeTe 3 and CrSiTe 3

Chen, Lebing [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000298298428)·Ye, Gaihua [Texas Tech Univ., Lubbock, TX (United States)]·Nnokwe, Cynthia [Texas Tech Univ., Lubbock, TX (United States)]·Pan, Xing-Chen [Tohoku Univ., Sendai (Japan)]·Tanigaki, Katsumi [Tohoku Univ., Sendai (Japan)]·Cheng, Guanghui [Tohoku Univ., Sendai (Japan); Purdue Univ., West Lafayette, IN (United States)]·Chen, Yong P. [Tohoku Univ., Sendai (Japan); Purdue Univ., West Lafayette, IN (United States); Aarhus Univ. (Denmark)] (ORCID:0000000273564179)·Yan, Jiaqiang [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000166254706)·Mandrus, David G. [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000336167104)·Llacsahuanga Allcca, Andres E. [Purdue Univ., West Lafayette, IN (United States)]·Giles-Donovan, Nathan [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)]·Birgeneau, Robert J. [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000311928333)·He, Rui [Texas Tech Univ., Lubbock, TX (United States)] (ORCID:0000000223687269)
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Abstract

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. Here 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 200K. 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 demonstrate that Raman scattering effectively probes high-frequency nonlinear phonon modes, offering insight into the generation of long-lived, tunable phonon frequency combs with potential applications in ultrafast material control and phonon-based technologies.

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36 MATERIALS SCIENCEfrequency combsnonlinear opticsraman spectroscopy

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Chen, Lebing [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000298298428), Ye, Gaihua [Texas Tech Univ., Lubbock, TX (United States)], Nnokwe, Cynthia [Texas Tech Univ., Lubbock, TX (United States)], Pan, Xing-Chen [Tohoku Univ., Sendai (Japan)], Tanigaki, Katsumi [Tohoku Univ., Sendai (Japan)], Cheng, Guanghui [Tohoku Univ., Sendai (Japan); Purdue Univ., West Lafayette, IN (United States)], Chen, Yong P. [Tohoku Univ., Sendai (Japan); Purdue Univ., West Lafayette, IN (United States); Aarhus Univ. (Denmark)] (ORCID:0000000273564179), Yan, Jiaqiang [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000166254706), Mandrus, David G. [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000336167104), Llacsahuanga Allcca, Andres E. [Purdue Univ., West Lafayette, IN (United States)], Giles-Donovan, Nathan [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)], Birgeneau, Robert J. [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000311928333), He, Rui [Texas Tech Univ., Lubbock, TX (United States)] (ORCID:0000000223687269). 2025-07-01. Spontaneously formed phonon frequency combs in van der Waals solid CrGeTe 3 and CrSiTe 3. https://doi.org/10.1038/s41467-025-61173-7

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