AI Article Synopsis

  • - Photonic time crystals are materials with dielectric properties that change periodically over time, much like how photonic crystals have spatially periodic properties.
  • - This study explores how, in the excitonic insulator TaNiSe, optical excitation leads to unique phonon states that result in photonic time crystalline behavior, characterized by periodic oscillations and enhanced terahertz (THz) reflectivity.
  • - The research demonstrates that the pumped TaNiSe can act as a gain medium for THz amplification, suggesting potential applications in THz communication by utilizing squeezed phonon noise.

Article Abstract

Photonic time crystals refer to materials whose dielectric properties are periodic in time, analogous to a photonic crystal whose dielectric properties is periodic in space. Here, we theoretically investigate photonic time-crystalline behaviour initiated by optical excitation above the electronic gap of the excitonic insulator candidate TaNiSe. We show that after electron photoexcitation, electron-phonon coupling leads to an unconventional squeezed phonon state, characterised by periodic oscillations of phonon fluctuations. Squeezing oscillations lead to photonic time crystalline behaviour. The key signature of the photonic time crystalline behaviour is terahertz (THz) amplification of reflectivity in a narrow frequency band. The theory is supported by experimental results on TaNiSe where photoexcitation with short pulses leads to enhanced THz reflectivity with the predicted features. We explain the key mechanism leading to THz amplification in terms of a simplified electron-phonon Hamiltonian motivated by ab-initio DFT calculations. Our theory suggests that the pumped TaNiSe is a gain medium, demonstrating that squeezed phonon noise may be used to create THz amplifiers in THz communication applications.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC11059354PMC
http://dx.doi.org/10.1038/s41467-024-47855-8DOI Listing

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