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Topological defects organize thermally excited vortical phonons in two-dimensional crystals

Wei-Shuo Lo, Yi-Jie Pang, Yi-Cheng Zhao, and Lin I*

  • *Contact author: lini@phy.ncu.edu.tw
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Phys. Rev. Research 8, 043015 – Published 5 October, 2026

DOI: https://doi.org/10.1103/8kgb-x8hr

Abstract

Thermal phonons in crystals are typically described in Fourier space, leaving open how disordered thermal vibrations are organized in real space-time. Recent work on two-dimensional crystals identified thermally excited vortical phonons—vorticity waves composed of traveling vortices with varying shapes and alternating-sign vorticity. Whether and how the dynamics of thermal vibrations can be organized by topological defects of vortex cores and saddles remain unclear. Here, using direct experiments on dusty plasma crystals and molecular-dynamics simulations of Yukawa crystals, we show that topological defects in the instantaneous velocity field organize thermally excited vortical phonons. In the Eulerian frame, slow-mode vorticity fluctuations are locally Gaussian yet develop coherent, intermittent, multiscale clusters of large vorticity-wave amplitude in space-time. In the Lagrangian frame, vortex cores display persistent superdiffusivelike transport together with concurrent evolution of core vorticity. Their kinetics obey robust topological rules, including charge-conserving pair creation and annihilation, exponential lifetime statistics, charge-dependent short-range correlations, and saddle-mediated splitting and merging of corotating vortices. These results move the description of thermal lattice vibrations beyond spectra alone and establish topological defects as organizing centers of thermally driven multiscale wave dynamics.

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Phys. Rev. Research 8, 043015– Published 5 October, 2026
  • Received 10 June 2026
  • Accepted 11 September 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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