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.

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

References in corpus (7)

• Evidence for an excitonic insulator phase in 1T-TiSe${}_2$
• Excitonic Bose-Einstein condensation in Ta2NiSe5 above room temperature
• Spontaneous exciton condensation in 1T-TiSe2: a BCS-like approach
• Models of coherent exciton condensation
• Spin excitations in the excitonic spin-density-wave state of the iron pnictides
• Electronic structure of PrCoO_3 and its temperature evolution
• Electric and magnetic multipoles and bond orders in excitonic insulators

Cited by in corpus (9)

• DFT+DMFT study on soft moment magnetism and covalent bonding in SrRu${}_2$O${}_6$
• 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
• Third-harmonic generation in excitonic insulators
• Strong enhancement of magnetic susceptibility induced by spin-nematic fluctuations in an excitonic insulating system with spin-orbit coupling
• Pressure-induced spin-state ordering in Sr${}_2$CoO${}_3$F
• Effects of magnetic fields and orbital angular momentum on excitonic condensation in two-orbital Hubbard model
• Emergence of pure spin current in doped excitonic magnets