Journal Article Magnetic Field Effects in a Correlated Electron System with Spin-State Degree of Freedom -Implication of an Excitonic Insulator-

Tatsuno, Taro  ,  那須, 譲治  ,  Nasu, Joji  ,  Mizoguchi, Eriko  ,  Naka, Makoto  ,  Ishihara, Sumio

85p.083706 , 2016-07 , The Physical Society of Japan
Magnetic field (H) effects on a correlated electron system with a spin-state degree of freedom are examined. The effective Hamiltonian derived from the two-orbital Hubbard model is analyzed by the mean-field approximation. Applying a magnetic field to the low-spin (LS) phase induces an excitonic insulating phase as well as a spin-state ordered phase where the LS and high-spin (HS) states are ordered alternately. When H is applied to the HS phase, a reentrant transition for the HS phase appears. A rich variety of the phase diagrams is attributed to the spin-state degree of freedom and their combinations in the wave function as well as in the real-space configuration. The present results provide a possible interpretation for the recent experimental observation of LaCoO3 under a strong magnetic field.

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