Ultrafast melting and recovery of collective order in the excitonic insulator Ta${}_2$NiSe${}_5$

Abstract

The layered chalcogenide Ta${}_2$NiSe${}_5$ has been proposed to host an excitonic condensate in its ground state, a phase that could offer a unique platform to study and manipulate many-body states at room temperature. However, identifying the dominant microscopic contribution to the observed spontaneous symmetry breaking remains challenging, perpetuating the debate over the ground state properties. Here, using broadband ultrafast spectroscopy we investigate the out-of-equilibrium dynamics of Ta${}_2$NiSe${}_5$ and demonstrate that the transient reflectivity in the near-infrared range is connected to the system's low-energy physics. We track the status of the ordered phase using this optical signature, establishing that high-fluence photoexcitations can suppress this order. From the sub-50 fs quenching timescale and the behaviour of the photoinduced coherent phonon modes, we conclude that electronic correlations provide a decisive contribution to the excitonic order formation. Our results pave the way towards the ultrafast control of an exciton condensate at room temperature.

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Cited by in corpus (17)

• Imaging the coherent propagation of collective modes in the excitonic insulator candidate Ta${}_2$NiSe${}_5$ at room temperature
• Photo-induced phase transition and associated time scales in the excitonic insulator Ta${}_2$NiSe${}_5$
• Lattice dynamics of the excitonic insulator Ta${}_2$Ni(Se${}_{1-x}$S${}_x$)${}_5$
• A New Era of Excitonic Insulators
• Disentangling lattice and electronic instabilities in the excitonic insulator candidate Ta${}_2$NiSe${}_5$ by nonequilibrium spectroscopy
• Ultrafast Switching from the Charge Density Wave Phase to a Metastable Metallic State in 1T-TiSe${}_2$
• Anomalous excitonic phase diagram in band-gap-tuned Ta2Ni(Se,S)5
• Terahertz parametric amplification as a reporter of exciton condensate dynamics
• Ultrafast charge carrier and exciton dynamics in an excitonic insulator probed by time-resolved photoemission spectroscopy
• Third-harmonic generation in excitonic insulators
• Theory of time-crystalline behaviour mediated by phonon squeezing in Ta2NiSe5
• Collective modes and Raman response in Ta${}_2$NiSe${}_5$
• Time, momentum, and energy resolved pump-probe tunneling spectroscopy of two-dimensional electron systems
• Detecting photoelectrons from spontaneously formed excitons
• 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${}_5$
• Probing the collective excitations of excitonic insulators in an optical cavity