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

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${}_5$.

arXiv comment13 pages, 10 figures

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Cited by in corpus (10)

• Role of electron-phonon coupling in excitonic insulator candidate Ta2NiSe5
• A New Era of Excitonic Insulators
• Effect of photoinduced screening on the spectroscopic signature of exciton-phonon coupling
• Collective modes and Raman response in Ta${}_2$NiSe${}_5$
• Hidden excitonic quantum states with broken time-reversal symmetry
• Ultrafast Raman thermometry in driven YBa${}_2$Cu${}_3$O${}_{6.48}$
• Identification of metastable lattice distortion free charge density wave at photoinduced interface via TRARPES
• Anomalous phonon Grüneisen parameters in semiconductor Ta${}_2$NiS${}_5$
• Gate tuning of coupled electronic and structural phase transition in atomically thin Ta${}_2$NiSe${}_5$
• Unveiling Excitonic Insulator Signatures in Ta${}_2$NiSe${}_5$