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Optical Studies of a Layered Manganite La_{1.2}Sr_{1.8}Mn_2O_7 : Polaron Correlation Effect

H. J. Lee·K. H. Kim·J. H. Jung·T. W. Noh·R. Suryanarayanan·G. Dhalenne·A. Revcolevschi
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Abstract

Optical conductivity spectra of a cleaved ab-plane of a La_{1.2}Sr_{1.8}Mn_2O_7 single crystal exhibit a small polaron absorption band in the mid-infrared region at overall temperatures. With decreasing temperature (T) to Curie temperature (T_C), the center frequency of the small polaron band moves to a higher frequency, resulting in a gap-like feature, and that it collapses to a lower frequency below T_C. Interestingly, with decreasing T, the stretching phonon mode hardens above T_C and softens below T_C. These concurring changes of lattice and electronic structure indicate that short range polaron correlation exist above T_C but disappear with a magnetic ordering.

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H. J. Lee, K. H. Kim, J. H. Jung, T. W. Noh, R. Suryanarayanan, G. Dhalenne, A. Revcolevschi. 2000-04-27. Optical Studies of a Layered Manganite La_{1.2}Sr_{1.8}Mn_2O_7 : Polaron Correlation Effect. https://doi.org/10.1103/physrevb.62.11320

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