Photo-excited Dynamics in the Excitonic Insulator Ta2NiSe5

Abstract

The excitonic insulator is an intriguing correlated electron phase formed of condensed excitons. A promising candidate is the small band gap semiconductor Ta2NiSe5. Here we investigate the quasiparticle and coherent phonon dynamics in Ta2NiSe5 in a time resolved pump probe experiment. Using the models originally developed by Kabanov et al. for superconductors, we show that the material's intrinsic gap can be described as almost temperature independent for temperatures up to about 250 K to 275 K. This behavior supports the existence of the excitonic insulator state in Ta2NiSe5. The onset of an additional temperature dependent component to the gap above these temperatures suggests that the material is located in the BEC-BCS crossover regime. Furthermore, we show that this state is very stable against strong photoexcitation, which reveals that the free charge carriers are unable to effectively screen the attractive Coulomb interaction between electrons and holes, likely due to the quasi one-dimensional structure of Ta2NiSe5.

arXiv comment27 pages, 8 figures

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Cited by in corpus (12)

• Photo-induced semimetallic states realised in electron-hole coupled insulators
• Photoinduced multistage phase transitions in Ta2NiSe5
• Ultrafast melting and recovery of collective order in the excitonic insulator Ta${}_2$NiSe${}_5$
• Orthorhombic-to-monoclinic transition in Ta${}_2$NiSe${}_5$ due to a zone-center optical phonon instability
• Pump driven normal-to-excitonic insulator transition: Josephson oscillations and signatures of BEC-BCS crossover in time-resolved ARPES
• Phononic soft mode and strong electronic background behavior across the structural phase transition in the excitonic insulator Ta${}_2$NiSe${}_5$ (with Erratum)
• Nonequilibrium dynamics in the pump-probe spectroscopy of excitonic insulators
• A New Era of Excitonic Insulators
• Terahertz parametric amplification as a reporter of exciton condensate dynamics
• Photoinduced electron-electron pairing in the extended Falicov-Kimball model
• Optical amplification in a CDW-phase of a quasi-two dimensional material
• Long-lived relaxation channel and exciton-phonon coupling in Ta2NiSe5 via non-degenerate pump-probe spectroscopy