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Imaging the coherent propagation of collective modes in the excitonic insulator Ta2NiSe5 at room temperature

Bretscher, HM and Andrich, P and Murakami, Y and Golež, D and Remez, B and Telang, P and Singh, A and Harnagea, L and Cooper, NR and Millis, AJ and Werner, P and Sood, AK and Rao, A (2021) Imaging the coherent propagation of collective modes in the excitonic insulator Ta2NiSe5 at room temperature. In: Science Advances, 7 (28).

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Official URL: https://doi.org/10.1126/sciadv.abd6147


Excitonic insulators host a condensate of electron-hole pairs at equilibrium, giving rise to collective many-body effects. Although several materials have emerged as excitonic insulator candidates, evidence of long-range coherence is lacking and the origin of the ordered phase in these systems remains controversial. Here, using ultrafast pump-probe microscopy, we investigate the possible excitonic insulator Ta2NiSe5. Below 328 K, we observe the anomalous micrometer-scale propagation of coherent modes at velocities of ~105 m/s, which we attribute to the hybridization between phonon modes and the phase mode of the condensate. We develop a theoretical framework to support this explanation and propose that electronic interactions provide a substantial contribution to the ordered phase in Ta2NiSe5. These results allow us to understand how the condensate's collective modes transport energy and interact with other degrees of freedom. Our study provides a unique paradigm for the investigation and manipulation of these properties in strongly correlated materials. Copyright

Item Type: Journal Article
Publication: Science Advances
Publisher: American Association for the Advancement of Science
Additional Information: The copyright for this article belongs to the author.
Keywords: Degrees of freedom (mechanics); Selenium compounds; Tantalum compounds, Coherent propagation; Electron hole pairs; Electronic interactions; Excitonic insulator; Many-body effect; Pump-probe microscopies; Strongly correlated materials; Theoretical framework, Nickel compounds, article; conceptual framework; degree of freedom; microscopy; phonon; room temperature; velocity
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 10 Aug 2023 11:27
Last Modified: 10 Aug 2023 11:27
URI: https://eprints.iisc.ac.in/id/eprint/82665

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