Broadband phonon-velocity suppression and a finite anisotropic crossover in twisted bilayer SnSe

[2608.15189] Broadband phonon-velocity suppression and a finite anisotropic crossover in twisted bilayer SnSe Skip to main content Search Submit Donate Log in Search arXiv Press Enter to search · Advanced search Condensed Matter > Materials Science arXiv:2608.15189 (cond-mat) [Submitted on 15 Aug 2026] Title: Broadband phonon-velocity suppression and a finite anisotropic crossover in twisted bilayer SnSe Authors: Peng Kang , Wei Yin , Da Wan , Shulin Bai , Sirui Fan , Qi Zou , Hongfeng Li , Xiao Xiang , Zhen Li , Yu Liu , Lei Zheng , Li-Dong Zhao View a PDF of the paper titled Broadband phonon-velocity suppression and a finite anisotropic crossover in twisted bilayer SnSe, by Peng Kang and 10 other authors View PDF HTML (experimental) Abstract: Moiré superlattices reshape lattice dynamics without altering chemical composition, yet how crystal anisotropy modifies this control remains unclear. We combine density-functional-theory (DFT)-calibrated lattice-dynamical calculations with angle-matched untwisted controls to study puckered bilayer SnSe across seven commensurate twist angles ($3.18^\circ$--$8.77^\circ$). At 300 K, twisting suppresses the band-path heat-capacity-weighted mean-square group velocity to 2.6--8.4\% of the control values; the suppression spans a broad frequency range rather than a few soft branches. The velocity response crosses over between $4.78^\circ$ and $3.82^\circ$ into a regime where the relaxed stacking textures and frequency-resolved velocity profiles become self-similar, with the normalized mean-square velocity ratio spanning only 11.1\% of its mean across the three smallest angles---a finite anisotropic crossover, not a singular-angle condition. Direct DFT--MACE force-constant agreement ($r=0.996$), uniform $4\times4\times1$ stability scans, and acoustic-sum-rule and path-density tests support the trend. The equilibrium trend is defined by six structures after excluding one relaxation-sensitive case. These results extend phonon twistronics to low-symmetry layered materials and identify crystal anisotropy as a key determinant of finite-angle phonon crossover behavior. Comments: 15 pages, 8 figures Subjects: Materials Science (cond-mat.mtrl-sci) ; Computational Physics (physics.comp-ph) Cite as: arXiv:2608.15189 [cond-mat.mtrl-sci] (or arXiv:2608.15189v1 [cond-mat.mtrl-sci] for this version) https://doi.org/10.48550/arXiv.2608.15189 Focus to learn more arXiv-issued DOI via DataCite Submission history From: Peng Kang PhD [ view email ] [v1] Sat, 15 Aug 2026 12:12:21 UTC (977 KB) Full-text links: Access Paper: View a PDF of the paper titled Broadband phonon-velocity suppression and a finite anisotropic crossover in twisted bilayer SnSe, by Peng Kang and 10 other authors View PDF HTML (experimental) TeX Source view license Current browse context: cond-mat.mtrl-sci < prev | next > new | recent | 2026-08 Change to browse by: cond-mat physics physics.comp-ph References & Citations NASA ADS Google Scholar Semantic Scholar export BibTeX citation Loading... BibTeX formatted citation × loading... 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