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arXiv · 2412.13329

Revealing the anisotropic charge-density-wave order of TiSe$_2$ through high harmonic generation

Lin Zhang·Igor Tyulnev·Lenard Vamos·Julita Poborska·Utso Bhattacharya·Ravindra W. Chhajlany·Tobias Grass·Jens Biegert·Maciej Lewenstein
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Abstract

Titanium diselenide (TiSe$_{2}$) is a transition-metal dichalcogenide material that undergoes a charge-density-wave (CDW) transition at $T_{c}\approx 200\,\mathrm{K}$. In a recent experiment [I. Tyulnev {\it et al.}, Commun. Mater. 6, 152 (2025)], the high harmonic generation (HHG) spectra of this material has been studied, which exhibits asymmetric behavior with respect to the polarization angle of the incident light and provides a new perspective to the CDW phase transition. In this work, we work out a theoretical explanation for the experimentally observed behavior of HHG spectra. We propose a simplified phenomenological mean-field model for this material, based on which the HHG spectra is calculated through the time-dependent Schr{\" o}dinger equation. This model correctly describes the measured intensity distribution of the third-, fifth-, and seventh-order harmonic generation as a function of polarization direction and reveals a strong asymmetry due to the anisotropic CDW order in the low temperature phase. Our work provides a basis for applying high harmonic spectroscopy to reveal a new perspective on the nature of CDW orders.

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Lin Zhang, Igor Tyulnev, Lenard Vamos, Julita Poborska, Utso Bhattacharya, Ravindra W. Chhajlany, Tobias Grass, Jens Biegert, Maciej Lewenstein. 2024-12-17. Revealing the anisotropic charge-density-wave order of TiSe$_2$ through high harmonic generation. https://doi.org/10.1103/812z-nl4m

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