发表机构
Posgrado en Ciencias Físicas, Universidad Nacional Autónoma de México; Depto. de Sistemas Complejos, Instituto de Física, Universidad Nacional Autónoma de México (UNAM)（墨西哥国立自治大学物理科学研究生院; 墨西哥国立自治大学物理研究所复杂系统系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过二聚化Fermi-Pasta-Ulam-Tsingou链的SSH模型，发现二聚化强度达到最大值一半时出现隔离阈值，该阈值由umklapp过程决定，声子隙可作为可调滤波器控制非线性晶格中的热化。
AI 中文摘要
在经典非简谐晶格中，驱动非线性模式混合的共振结构会被带隙重塑。然而，谱隙是阻碍还是促进长时间热化仍不清楚。在此，我们研究了一条二聚化的Fermi-Pasta-Ulam-Tsingou链——一个具有交替弹簧常数的经典SSH模型类似物——并量化了声学-光学能隙如何在α型（三次方）非线性下控制弛豫。通过长时间辛模拟追踪模态能量和谱熵，我们发现当二聚化强度达到其最大值的一半时，会出现一个尖锐的隔离阈值，该阈值由第一个umklapp过程的起始决定，该过程允许两个区边界声学声子融合成一个区中心光学声子；低于此阈值，三波声学-声学-光学散射在约1e4振荡周期的时间尺度上激活光学支，而高于此阈值，能带保持动态隔离。我们进一步表明，边界条件重塑了这一图景，对特定模式激发产生长寿命的粘性态。这些结果确立了声子隙作为非线性能量输运的可调、动量选择性滤波器，为控制二聚化或拓扑有隙非线性晶格中的热化提供了一条通用途径。
英文摘要
In classical anharmonic lattices, the resonance structure driving nonlinear mode mixing is reshaped by band gaps. However, it remains unclear whether a spectral gap hinders or promotes long-time thermalization. Here we study a dimerized Fermi-Pasta-Ulam-Tsingou chain - a classical SSH model analogue with alternating spring constants - and quantify how the acoustic-optical gap controls relaxation under alpha-type (cubic) nonlinearity. Tracking modal energies and spectral entropy via long-time symplectic simulations, we find a sharp isolation threshold when the dimerization strength reaches half its maximum value, set by the onset of the first umklapp process that allows two zone-boundary acoustic phonons to fuse into a zone-center optical phonon; below this threshold, three-wave acoustic-acoustic-optical scattering activates the optical branch on timescales of order 1e4 oscillation periods, while above it the bands remain dynamically isolated. We further show that boundary conditions reshape this picture, producing long-lived sticky states for specific mode excitations. These results establish the phononic gap as a tunable, momentum-selective filter for nonlinear energy transport, suggesting a general route to controlling thermalization in dimerized or topologically gapped nonlinear lattices.
CommentsUnder review for Physical Review E
