Charge density waves condensate as measure of charge order and disorder in Eu_(1-x)Sr_xMn0_3 (x = 0.50, 0.58) manganites

摘要

We have explored the low-energy excitations in epitaxial thin films of Eu_(1-x)Sr)_xMn0_3 [x = 0.50: spin-glass with short range charge-order and x = 0.58: long range charge-order] using terahertz time-domain spectroscopy. A finite frequency peak structure in optical conductivity is observed at ~3.5 meV for both the films. While peak structure of x = 0.58 film possesses distinct properties of low-energy collective excitations of charge-density waves, the same is subtle and shallower with weaker peak conductivity for x = 0.50 film. These data, corroborated by magnetization, provide unambiguous evidence of the effect of range of charge-ordering, pinning, and disorder (induced by spin-glass state) on the manifestation of charge-density waves.