Ultrafast melting and recovery of collective order in the excitonic insulator Ta<sub>2</sub>NiSe<sub>5</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33727541.
- Also identified by DOI 10.1038/s41467-021-21929-3 and PMC identifier 7966769.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The layered chalcogenide Ta<sub>2</sub>NiSe<sub>5</sub> 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<sub>2</sub>NiSe<sub>5</sub> 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.