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

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. 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.

22 pages, 10 figures

References in corpus (18)

• Discovery of intrinsic ferromagnetism in 2D van der Waals crystals
• Frequency comb spectroscopy
• Metastable ferroelectricity in optically strained $SrTi{O}_3$
• An effective magnetic field from optically driven phonons
• The Fermi-Pasta-Ulam problem: 50 years of progress
• Hyperfine phononic frequency comb
• Phononic frequency comb via three-mode parametric three-wave mixing
• Tricritical behavior of two-dimensional intrinsic ferromagnetic semiconducting CrGeTe3
• Phononic Frequency Combs via Nonlinear Resonances
• Magnetic field-induced quantum phase transitions in a van der Waals magnet
• Terahertz phonon engineering with van der Waals heterostructures
• Evidence of spin-phonon coupling in CrSiTe${}_3$
• First-principles studies of spin-phonon coupling in Cr2Ge2Te6 monolayer
• Pressure-Induced Structural Phase Transition and a Special Amorphization Phase of Two-Dimensional Ferromagnetic Semiconductor Cr2Ge2Te6
• A Raman study of the temperature and magnetic field dependence of electronic and lattice properties in MnSi
• Anisotropic magnon damping by zero-temperature quantum fluctuations in ferromagnetic CrGeTe${}_3$
• Dimensional crossover in a layered ferromagnet detected by spin correlation driven distortions
• Echoes in a Single Quantum Kerr-nonlinear Oscillator

Cited by in corpus (1)

• Phonon frequency comb close to an isolated Einstein mode in InSiTe3