Strong interband interaction in the excitonic insulator phase of Ta${}_2$NiSe${}_5$

Abstract

Excitonic insulator (EI) was proposed in 60's as a distinct insulating state originating from pure electronic interaction, but its material realization has been elusive with extremely few material candidates and with only limited evidence such as anomalies in transport properties, band dispersions, or optical transitions. We investigate the real-space electronic states of the low temperature phase in Ta${}_2$NiSe${}_5$ with an atomic resolution to clearly identify the quasiparticle energy gap together with the strong electron-hole band renormalization using scanning tunneling microscopy (STM) and spectroscopy (STS). These results are in good agreement with the EI transition scenario in Ta${}_2$NiSe${}_5$. Our spatially-resolved STS data and theoretical calculations reveal further the orbital inversion at band edges, which indicates the exciton condensation close to the Bardeen-Cooper-Schrieffer regime.

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Cited by in corpus (25)

• Nature of symmetry breaking at the excitonic insulator transition: Ta${}_2$NiSe${}_5$
• Direct observation of excitonic instability in Ta2NiSe5
• Band hybridisation at the semimetal-semiconductor transition of Ta${}_2$NiSe${}_5$ enabled by mirror-symmetry breaking
• Non-Coulomb strong electron-hole binding in $T{a}_{2}NiS{e}_5$ revealed by time- and angle-resolved photoemission spectroscopy
• Detecting electron-phonon couplings during photo-induced phase transition
• Orthorhombic-to-monoclinic transition in Ta${}_2$NiSe${}_5$ due to a zone-center optical phonon instability
• Phononic soft mode and strong electronic background behavior across the structural phase transition in the excitonic insulator Ta${}_2$NiSe${}_5$ (with Erratum)
• Critical charge fluctuations and emergent coherence in a strongly correlated excitonic insulator
• Role of electron-phonon coupling in excitonic insulator candidate Ta2NiSe5
• Doping-controlled transition from excitonic insulator to semimetal in Ta${}_2$NiSe${}_5$
• A New Era of Excitonic Insulators
• Anomalous excitonic phase diagram in band-gap-tuned Ta2Ni(Se,S)5
• Terahertz parametric amplification as a reporter of exciton condensate dynamics
• Tunneling-tip-induced collapse of the charge gap in the excitonic insulator Ta${}_2$NiSe${}_5$
• Evolution of the electronic structure in Ta${}_2$NiSe${}_5$ across the structural transition revealed by resonant inelastic x-ray scattering
• Finite-temperature photoemission in the extended Falicov-Kimball model: a case study for Ta${}_2$NiSe${}_5$
• Effects of Disorder on the Transport of Collective Modes in an Excitonic Condensate
• Pressure suppression of the excitonic insulator state in Ta2NiSe5 observed by optical conductivity
• An On-Site Density Matrix Description of the Extended Falicov--Kimball Model at Finite Temperatures
• Theory of time-crystalline behaviour mediated by phonon squeezing in Ta2NiSe5
• Third-harmonic generation in excitonic insulators
• Theory of Thermal Conductivity on Excitonic Insulator
• Detecting photoelectrons from spontaneously formed excitons
• Gate tuning of coupled electronic and structural phase transition in atomically thin Ta${}_2$NiSe${}_5$
• Unveiling Excitonic Insulator Signatures in Ta${}_2$NiSe${}_5$