Optically Induced Symmetry Breaking Due to Nonequilibrium Steady State Formation in Charge Density Wave Material 1T-TiSe<sub>2</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 37812066.
- Also identified by DOI 10.1021/acs.nanolett.3c03736.
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Abstract
The strongly correlated charge density wave (CDW) phase of 1T-TiSe<sub>2</sub> is of interest to verify the claims of a chiral order parameter. Characterization of the symmetries of 1T-TiSe<sub>2</sub> is critical to understand the origin of its intriguing properties. Here we use very low-power, continuous wave laser excitation to probe the symmetries of 1T-TiSe<sub>2</sub> by using the circular photogalvanic effect. We observe that the ground state of the CDW phase (<i>D</i><sub>3<i>d</i></sub>) is achiral. However, laser excitation above a threshold intensity transforms 1T-TiSe<sub>2</sub> into a nonequilibrium chiral phase (<i>C</i><sub>3</sub>), which changes the electronic correlations in the material. The inherent sensitivity of the photogalvanic technique to structural symmetries provides evidence of the different optically driven phase of 1T-TiSe<sub>2</sub>, which allows us to assign symmetry groups to these states. Our work demonstrates that optically induced phase change can occur at extremely low optical intensities in strongly correlated materials, providing a pathway to engineer new phases using light.