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At least 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Polarization-dependent infrared reflectivity study of Sr 2.5 Ca 11.5 Cu 24 O 41 under pressure: Charge dynamics, charge distribution, and anisotropy

We present a polarization-dependent infrared reflectivity study of the spin-ladder compound Sr₂̣₅Ca₁₁̣₅Cu₂₄O₄₁ under pressure. The optical response is strongly anisotropic, with the highest reflectivity along the ladders/chains ( E ∥c) revealing a metallic character. For the polarization direction perpendicular to the ladder plane, an insulating behavior is observed. With increasing pressure the optical conductivity for E ∥c shows a strong increase, which is most pronounced below 2000cm⁻¹. According to the spectral weight analysis of the E ∥c optical conductivity the hole concentration in the ladders increases with increasing pressure and tends to saturate at high pressure. At ~7.5 GPa the number of holes per Cu atom in the ladders has increased by Δδ=0.09(±0.01), and the Cu valence in the ladders has reached the value +2.33. Thus, the optical data suggest that Sr₂̣₅Ca₁₁̣₅Cu₂₄O₄₁ remains electronically highly anisotropic up to high pressure, also at low temperatures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗