Role of electron-phonon coupling in excitonic insulator candidate Ta2NiSe5

Abstract

Electron-hole bound pairs, or excitons, are common excitations in semiconductors. They can spontaneously form and ``condense'' into a new insulating ground state -- the so-called excitonic insulator -- when the energy of electron-hole Coulomb attraction exceeds the band gap. In the presence of electron-phonon coupling, a periodic lattice distortion often concomitantly occurs with this exciton condensation. However, similar structural transition can also be induced by electron-phonon coupling itself, therefore hindering the clean identification of bulk excitonic insulators based on reductionistic reasoning (e.g. which instability is the ``driving force'' of the phase transition). Using high-resolution synchrotron x-ray diffraction and angle-resolved photoemission spectroscopy techniques, we identify key electron-phonon coupling effects in a leading excitonic insulator candidate Ta2NiSe5. These include an extensive unidirectional lattice fluctuation and an electronic pseudogap in the normal state, as well as a negative electronic compressibility in the charge-doped broken-symmetry state. In combination with first principles and model calculations, we determine a minimal lattice model and the corresponding interaction parameters that capture the experimental observations. More importantly, we show how the Coulomb and electron-phonon coupling effects can be separated on the level of lattice model, and demonstrate a general framework beyond the reductionist approach in the investigation of correlated systems with intertwined orders.

arXiv comment18 pages, 12 + 4 figures

References in corpus (41)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• The pseudogap in high-temperature superconductors: an experimental survey
• Electron-phonon interactions from first principles
• Nematic order in iron superconductors - who is in the driver's seat?
• Theory of Intertwined Orders in High Temperature Superconductors
• Divergent nematic susceptibility in an iron arsenide superconductor
• Electronic structure of quantum materials studied by angle-resolved photoemission spectroscopy
• Nonthermal pathways to ultrafast control in quantum materials
• Signatures of exciton condensation in a transition metal dichalcogenide
• Singular quasiparticle scattering in the proximity of charge instabilities
• Classification of Charge Density Waves Based on Their Nature
• Pseudogap and charge density waves in two dimensions
• Orthorhombic-to-Monoclinic Phase Transition of Ta2NiSe5 Induced by the Bose-Einstein Condensation of Excitons
• Ultrafast Electronic Band Gap Control in an Excitonic Insulator
• Excitonic Bose-Einstein condensation in Ta2NiSe5 above room temperature
• Emergence of coherence in the charge-density wave state of 2H-NbSe${}_2$
• Anomalously Strong Near-Neighbor Attraction in Doped 1D Cuprate Chains
• Nature of symmetry breaking at the excitonic insulator transition: Ta${}_2$NiSe${}_5$
• Electron-Phonon Coupling from $\text{Ab Initio}$ Linear-Response Theory within the $GW$ Method: Correlation-Enhanced Interactions and Superconductivity in Ba${}_{1-x}$K${}_x$BiO${}_3$
• The Electron-Phonon Interaction in the Presence of Strong Correlations
• Giant exciton Fano resonance in quasi-one-dimensional Ta${}_2$NiSe${}_5$
• Photo-induced semimetallic states realised in electron-hole coupled insulators
• Direct observation of excitonic instability in Ta2NiSe5
• Photo-induced enhancement of excitonic order
• Electron-Phonon Coupling Mode in Excitonic Insulator
• Band hybridisation at the semimetal-semiconductor transition of Ta${}_2$NiSe${}_5$ enabled by mirror-symmetry breaking
• Strong interband interaction in the excitonic insulator phase of Ta${}_2$NiSe${}_5$
• Non-Coulomb strong electron-hole binding in $T{a}_{2}NiS{e}_5$ revealed by time- and angle-resolved photoemission spectroscopy
• Inhibition of the photoinduced structural phase transition in the excitonic insulator Ta${}_2$NiSe${}_5$
• Photoinduced multistage phase transitions in Ta2NiSe5
• Spectroscopic evidence for negative electronic compressibility in a quasi-three-dimensional spin-orbit correlated metal
• 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
• Superconducting fluctuations in overdoped Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$
• Doping-controlled transition from excitonic insulator to semimetal in Ta${}_2$NiSe${}_5$
• Crossed Luttinger Liquid Hidden in a Quasi-two-dimensional Material η-Mo4O11
• Disentangling lattice and electronic instabilities in the excitonic insulator candidate Ta${}_2$NiSe${}_5$ by nonequilibrium spectroscopy
• Revealing the Coulomb interaction strength in a cuprate superconductor
• Exciton dynamics uncovering electron fractionalization in superconducting cuprates
• Ultrafast charge carrier and exciton dynamics in an excitonic insulator probed by time-resolved photoemission spectroscopy
• Detecting photoelectrons from spontaneously formed excitons

Cited by in corpus (13)

• A New Era of Excitonic Insulators
• Spontaneous gap opening and potential excitonic states in an ideal Dirac semimetal Ta${}_2$Pd${}_3$Te${}_5$
• Evidence for an Excitonic Insulator State in Ta${}_2$Pd${}_3$Te${}_5$
• Signatures of Mode-Resolved, Nonlocal Electron-Phonon Coupling in Two-Dimensional Spectroscopy
• Entanglement Witness for Indistinguishable Electrons using Solid-State Spectroscopy
• Persistence of charge ordering instability to Coulomb engineering in the excitonic insulator candidate TiSe${}_2$
• Detecting Thermodynamic Phase Transition via Explainable Machine Learning of Photoemission Spectroscopy
• 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${}_5$
• Strong long-wavelength electron-phonon coupling in Ta${}_2$Ni(Se,S)${}_5$
• Unveiling Excitonic Insulator Signatures in Ta${}_2$NiSe${}_5$
• Excitons and Optical Response in Excitonic Insulator Candidate TiSe${}_2$
• Light Control of Triplet Pairing in Correlated Electrons with Mixed-Sign Interactions