Evidence for topological defects in a photoinduced phase transition
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Evidence for topological defects in a photoinduced phase transition

  • Author(s): Zong, Alfred;
  • Kogar, Anshul;
  • Bie, Ya-Qing;
  • Rohwer, Timm;
  • Lee, Changmin;
  • Baldini, Edoardo;
  • Ergecen, Emre;
  • Yilmaz, Mehmet B;
  • Freelon, Byron;
  • Sie, Edbert J;
  • Zhou, Hengyun;
  • Straquadine, Joshua;
  • Walmsley, Philip;
  • Dolgirev, Pavel E;
  • Rozhkov, Alexander V;
  • Fisher, Ian R;
  • Jarillo-Herrero, Pablo;
  • Fine, Boris V;
  • Gedik, Nuh
  • et al.
Abstract

Upon excitation with an intense ultrafast laser pulse, a symmetry-broken ground state can undergo a non-equilibrium phase transition through pathways dissimilar from those in thermal equilibrium. Determining the mechanism underlying these photo-induced phase transitions (PIPTs) has been a long-standing issue in the study of condensed matter systems. To this end, we investigate the light-induced melting of a unidirectional charge density wave (CDW) material, LaTe$_3$. Using a suite of time-resolved probes, we independently track the amplitude and phase dynamics of the CDW. We find that a quick ($\sim\,$1$\,$ps) recovery of the CDW amplitude is followed by a slower reestablishment of phase coherence. This longer timescale is dictated by the presence of topological defects: long-range order (LRO) is inhibited and is only restored when the defects annihilate. Our results provide a framework for understanding other PIPTs by identifying the generation of defects as a governing mechanism.

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