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

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.

4 pages including 5 figures. submitted to Phys. Rev. B

References in corpus (3)

• Charge melting and polaron collapse in $L{a}_{1.2}S{r}_{1.8}M{n}_2{O}_7$
• Self-trapped Exciton and Franck-Condon Spectra Predicted in LaMnO${}_3$
• Lattice Displacements Above Tc in the Layered Manganite La1.2Sr1.8Mn2O7

Cited by in corpus (4)

• Optical Evidence of Multiphase Coexistence in Single Crystalline (La,Pr,Ca)MnO3
• Magneto-optical investigation of the field-induced spin-glass insulator to ferromagnetic metallic transition of the bilayer manganite (La${}_{0.4}$Pr${}_{0.6}$)${}_{1.2}$Sr${}_{1.8}$Mn${}_2$O${}_7$
• Observation of electronic inhomogeneity and charge density wave in a bilayer La${}_{1.36}$Sr${}_{1.64}$Mn${}_2$O${}_7$ single crystal
• Excitations across the equilibrium and photoinduced `hidden' states of magnetoresistive manganites