<p>Phase singularities—points carrying quantized topological charge—are universal features found across diverse wave systems from superfluids and superconductors to acoustic and optical fields<sup><CitationRef AdditionalCitationIDS="CR2 CR3" CitationID="CR1">1</CitationRef>–<CitationRef CitationID="CR4">4</CitationRef></sup>. Ensembles of these singularities exhibit distance correlations resembling particles in liquids<sup><CitationRef AdditionalCitationIDS="CR6 CR7" CitationID="CR5">5</CitationRef>–<CitationRef CitationID="CR8">8</CitationRef></sup>, extensively studied for their role in exotic material phases<sup><CitationRef AdditionalCitationIDS="CR10" CitationID="CR9">9</CitationRef>–<CitationRef CitationID="CR11">11</CitationRef></sup>. By contrast, the full correlations in phase space that govern the system evolution have remained unexplored and experimentally inaccessible. Here we directly measure the ultrafast dynamics of optical singularity ensembles, capturing their full phase-space correlations, presenting the joint distance–velocity distribution. Our observations show a breakdown of the particle-singularity analogy<sup><CitationRef CitationID="CR12">12</CitationRef></sup>: phase singularities accelerate towards formally divergent velocities in the moment before annihilation<sup><CitationRef CitationID="CR7">7</CitationRef>,<CitationRef CitationID="CR13">13</CitationRef>,<CitationRef CitationID="CR14">14</CitationRef></sup>, indicated by measurements of velocities exceeding the speed of light. These apparent superluminal velocities are paradoxically amplified by the slow group velocity of hyperbolic phonon polaritons in our material platform, hexagonal boron nitride membranes<sup><CitationRef AdditionalCitationIDS="CR16 CR17 CR18" CitationID="CR15">15</CitationRef>–<CitationRef CitationID="CR19">19</CitationRef></sup>. We demonstrate these phenomena using combined hardware and algorithmic advances in ultrafast electron microscopy<sup><CitationRef CitationID="CR18">18</CitationRef>,<CitationRef AdditionalCitationIDS="CR21 CR22 CR23 CR24" CitationID="CR20">20</CitationRef>–<CitationRef CitationID="CR25">25</CitationRef></sup>, achieving spatial and temporal resolutions, each an order of magnitude below the polaritonic wavelength and cycle period. Our findings deepen our understanding of phase singularities and their universality, enabling to probe topological defect dynamics at previously unattainable timescales.</p>

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Superluminal correlations in ensembles of optical phase singularities

  • T. Bucher,
  • A. Gorlach,
  • A. Niedermayr,
  • Q. Yan,
  • H. Nahari,
  • K. Wang,
  • R. Ruimy,
  • Y. Adiv,
  • M. Yannai,
  • T. L. Abudi,
  • E. Janzen,
  • C. Spaegele,
  • C. Roques-Carmes,
  • J. H. Edgar,
  • F. H. L. Koppens,
  • G. M. Vanacore,
  • H. H. Sheinfux,
  • S. Tsesses,
  • I. Kaminer

摘要

Phase singularities—points carrying quantized topological charge—are universal features found across diverse wave systems from superfluids and superconductors to acoustic and optical fields14. Ensembles of these singularities exhibit distance correlations resembling particles in liquids58, extensively studied for their role in exotic material phases911. By contrast, the full correlations in phase space that govern the system evolution have remained unexplored and experimentally inaccessible. Here we directly measure the ultrafast dynamics of optical singularity ensembles, capturing their full phase-space correlations, presenting the joint distance–velocity distribution. Our observations show a breakdown of the particle-singularity analogy12: phase singularities accelerate towards formally divergent velocities in the moment before annihilation7,13,14, indicated by measurements of velocities exceeding the speed of light. These apparent superluminal velocities are paradoxically amplified by the slow group velocity of hyperbolic phonon polaritons in our material platform, hexagonal boron nitride membranes1519. We demonstrate these phenomena using combined hardware and algorithmic advances in ultrafast electron microscopy18,2025, achieving spatial and temporal resolutions, each an order of magnitude below the polaritonic wavelength and cycle period. Our findings deepen our understanding of phase singularities and their universality, enabling to probe topological defect dynamics at previously unattainable timescales.