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arXiv · 2211.08537

Disentangling lattice and electronic instabilities in the excitonic insulator candidate Ta$_2$NiSe$_5$ by nonequilibrium spectroscopy

Kota Katsumi·Alexandr Alekhin·Sofia-Michaela Souliou·Michael Merz·Amir-Abbas Haghighirad·Matthieu Le Tacon·Sarah Houver·Maximilien Cazayous·Alain Sacuto·Yann Gallais
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Abstract

Ta$_2$NiSe$_5$ is an excitonic insulator candidate showing the semiconductor/semimetal-to-insulator (SI) transition below $T_{\text{c}}$ = 326 K. However, since a structural transition accompanies the SI transition, deciphering the role of electronic and lattice degrees of freedom in driving the SI transition has remained controversial. Here, we investigate the photoexcited nonequilibrium state in Ta$_2$NiSe$_5$ using pump-probe Raman and photoluminescence (PL) spectroscopies. The combined nonequilibrium spectroscopic measurements of the lattice and electronic states reveal the presence of a photoexcited metastable state where the insulating gap is suppressed, but the low-temperature structural distortion is preserved. We conclude that electron correlations play a vital role in the SI transition of Ta$_2$NiSe$_5$.

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Kota Katsumi, Alexandr Alekhin, Sofia-Michaela Souliou, Michael Merz, Amir-Abbas Haghighirad, Matthieu Le Tacon, Sarah Houver, Maximilien Cazayous, Alain Sacuto, Yann Gallais. 2022-11-15. Disentangling lattice and electronic instabilities in the excitonic insulator candidate Ta$_2$NiSe$_5$ by nonequilibrium spectroscopy. https://doi.org/10.1103/physrevlett.130.106904

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