Low-energy excitation spectra in the excitonic phase of cobalt oxides

Abstract

We study the excitonic phase and low-energy excitation spectra of perovskite cobalt oxides. Constructing the five-orbital Hubbard model defined on the three-dimensional cubic lattice for the $3d$ bands of Pr${}_{0.5}$Ca${}_{0.5}$CoO${}_3$, we calculate the excitonic susceptibility in the normal state in the random-phase approximation (RPA) to show the presence of the instability toward excitonic condensation. Based on the excitonic ground state with a magnetic multipole obtained in the mean-field approximation, we calculate the dynamical susceptibility of the excitonic phase in the RPA and find that there appear the gapless collective excitation in the spin-transverse mode (Goldstone mode) and the gapful collective excitation in the spin-longitudinal mode (Higgs mode). Experimental relevance is discussed.

arXiv comment5 pages, 4 figures, to be published in J. Phys. Soc. Jpn

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• Excitonic dispersion of the intermediate-spin state in LaCoO${}_3$ revealed by resonant inelastic X-ray scattering
• A New Era of Excitonic Insulators
• Excitonic Insulator State of the Extended Falicov-Kimball Model in the Cluster Dynamical Impurity Approximation
• Competing phases in a model of Pr-based cobaltites
• Excitonic magnet in external field: complex order parameter and spin currents
• Third-harmonic generation in excitonic insulators
• Theoretical investigation of excitonic magnetism in LaSrCoO${}_4$
• Spin texture and spin current in excitonic phases of the two-band Hubbard model
• Pressure-induced spin-state ordering in Sr${}_2$CoO${}_3$F
• Strong enhancement of magnetic susceptibility induced by spin-nematic fluctuations in an excitonic insulating system with spin-orbit coupling
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• Effects of magnetic fields and orbital angular momentum on excitonic condensation in two-orbital Hubbard model
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• Metal-insulator transition in CaCu${}_3$Fe${}_4$O${}_{12}$