Microscopic quantum interference in excitonic condensation of Ta${}_2$NiSe${}_5$

Abstract

The microscopic quantum interference associated with excitonic condensation in Ta${}_2$NiSe${}_5$ is studied in the BCS-type mean-field approximation. We show that in ultrasonic attenuation the coherence peak appears just below the transition temperature $T_{\mathrm{c}}$ whereas in NMR spin-lattice relaxation the rate rapidly decreases below $T_{\mathrm{c}}$; these observations can offer a crucial experimental test for the validity of the excitonic condensation scenario in Ta${}_2$NiSe${}_5$. We also show that the excitonic condensation manifests itself in a jump of the heat capacity at $T_{\mathrm{c}}$ as well as in softening of the elastic shear constant, in accordance with the second-order phase transition observed in Ta${}_2$NiSe${}_5$.

5 pages, 3 figures, Supplemental Material

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• Exciton-phonon cooperative mechanism of the triple-$q$ charge-density-wave and antiferroelectric electron polarization in TiSe${}_2$
• Orthorhombic-to-monoclinic transition in Ta${}_2$NiSe${}_5$ due to a zone-center optical phonon instability
• A New Era of Excitonic Insulators
• Nonequilibrium dynamics in the pump-probe spectroscopy of excitonic insulators
• FFLO Excitonic State in the Three-Chain Hubbard Model for Ta${}_2$NiSe${}_5$
• Disentangling lattice and electronic instabilities in the excitonic insulator candidate Ta${}_2$NiSe${}_5$ by nonequilibrium spectroscopy
• Electric and magnetic multipoles and bond orders in excitonic insulators
• Orbital diamagnetic susceptibility in excitonic condensation phase
• Photoinduced electron-electron pairing in the extended Falicov-Kimball model
• Excitonic Insulator State of the Extended Falicov-Kimball Model in the Cluster Dynamical Impurity Approximation
• Effects of Disorder on the Transport of Collective Modes in an Excitonic Condensate
• Excitonic Phase Diagram of the Three-Chain Hubbard Model for Semiconducting and Semimetallic Ta${}_2$NiSe${}_5$
• Theory of Orbital Susceptibility on Excitonic Insulator
• First- and second-order phase transitions between the uniform and FFLO excitonic states in the three-chain Hubbard model for Ta2NiSe5
• Spin texture and spin current in excitonic phases of the two-band Hubbard model
• Collective modes and Raman response in Ta${}_2$NiSe${}_5$
• FFLO Superconductivity Mediated by Excitonic Fluctuation in Semimetallic Ta${}_2$NiSe${}_5$
• Photo-induced Dynamics of Quasicrystalline Excitonic Insulator
• Elastic Soft Mode and Electric Quadrupole Response in Excitonic Insulator Candidate (Ta${}_{0.952}$V${}_{0.048}$)${}_2$NiSe${}_5$: Contribution of Electron-Phonon Interaction
• Unveiling Excitonic Insulator Signatures in Ta${}_2$NiSe${}_5$