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arXiv · 2602.03996

Tuning Terahertz Optomechanics of MoS2 Bilayers with Homogeneous In-plane Strain

S. Patel·Jose D. Mella·S. Puri·Salvador Barraza-Lopez·H. Nakamura
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Abstract

Homogeneous in-plane biaxial tensile strain strengthens the out-of-plane van der Waals (vdW) interaction in \MoS\ bilayers (BLs) and can be used to fine-tune their terahertz (THz) oscillations. Using ultralow-frequency Raman spectroscopy on hexagonal (2H) and rhombohedral (2R) stacked BLs, we observe a hardening of the interlayer breathing modes originating from a strain-induced Poisson contraction of the vdW separation between the layers characterized by an effective out-of-plane Poisson's ratio of $\nu_\mathrm{eff} \approx 0.19\text{--}0.24$. Strikingly, this geometric contraction drives the system into a highly repulsive regime of the intermolecular potential, corresponding to a Gr\"uneisen parameter of $\gamma \approx 14\text{--}20$. This value surpasses even the `giant' one reported for phosphorene, establishing these van der Waals BLs as highly tunable nonlinear mechanical platforms that can be addressed at the THz regime without external pressure knobs.

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S. Patel, Jose D. Mella, S. Puri, Salvador Barraza-Lopez, H. Nakamura. 2026-02-03. Tuning Terahertz Optomechanics of MoS2 Bilayers with Homogeneous In-plane Strain. https://doi.org/10.1103/5z5x-vyb5

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