Optical Conductivity Of Colossal-Magnetoresistance Compounds: Role Of Orbital Degeneracy In The Ferromagnetic Phase
PHYSICAL REVIEW B(1999)
摘要
Recent optical conductivity sigma(omega) experiments have revealed anomalous spectral distribution in the ferromagnetic phase of the perovskite system La1-xSrxMnO3. Using finite-temperature diagonalization techniques we investigate ate) for a model that contains only the e(g),-orbital degrees of freedom. Due to strong correlations the orbital model appears as a generalized t-J model with anisotropic interactions and three-site hopping. In the orbital t-J model sigma(omega) is characterized by a broad incoherent spectrum with increasing intensity as temperature is lowered, and a Drude peak with small weight, consistent with experiment. Our calculations for two-dimensional systems, which may have some particular relevance for the double-layer manganites, show that the scattering from orbital fluctuations can explain the order of magnitude of the incoherent part of sigma(omega) in the low-temperature ferromagnetic phase. Moreover, orbital correlation functions are studied and it is shown that x(2)-y(2) orbital order is preferred in the doped planar model at low temperature. [S0163-1829(99)01809-3].
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关键词
double layer,spectrum,correlation function,inelastic neutron scattering,degree of freedom
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