Abstract
Recent experiments have shown that the high-temperature incommensurate (I) charge density wave (CDW) phase of 1T-TaS 2 can be photoinduced from the lower-temperature, nearly commensurate CDW state. In a first step, several independent regions exhibiting I-CDW phase modulations nucleate and grow. After coalescence, these regions form a multidomain I-CDW phase that undergoes coarsening dynamics, i.e. a progressive increase of the domain size or I-CDW correlation length. Using time-resolved X-ray diffraction, we show that the wave vector of the photoinduced I-CDW phase is shorter than in the I-CDW phase at equilibrium, and progressively increases towards its equilibrium value as the correlation length increases. We interpret this behaviour as a consequence of a self-doping of the photoinduced I-CDW, following the presence of trapped electrons in the vicinity of CDW dislocation sites. Putting together results of the present and past experiments, we develop a scenario in which the I-CDW dislocations are created during the coalescence of the I-CDW phase regions.
Highlights
The physics of correlated materials involves couplings between charge, orbital, spin and lattice degrees of freedom, which give rise to a wealth of physical properties as well as complex phase diagrams [1, 2]
No contribution is observed before laser excitation, which is expected since the sample lies in its nearly commensurate (NC)-Charge density wave (CDW) phase
The photoinduced I*-CDW phase appears in the form of nuclei which subsequently grow
Summary
The physics of correlated materials involves couplings between charge, orbital, spin and lattice degrees of freedom, which give rise to a wealth of physical properties as well as complex phase diagrams [1, 2]. In layered CDW compounds such as rare-earth tritellurides and transition-metal dichalcogenides, photoinduced developments of CDW orders were reported [28,29,30,31,32,33,34,35,36,37] These photoinduced CDW orders were found to be either closely related to the ones observed at equilibrium [28,29,30,31,32,33,34] or genuinely new states of matter [35,36,37]. Their observation has highlighted an unforeseen complexity of the free energy surface of such layered materials, and the possibility of controlling transitions between several competing states by light
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