0.7 eV excitation in YBa₂Cu₃O_{7- delta}: evidence from epitaxial thin film and powder samples

Abstract

AbslmcLWe have measured the optical absorption speclrum of YBa2Cb01-6 crystalline thin films and powders in the range 2013) 10 10000 ."I.A broad absorption band near 5500 cm-' (0.7 eV) b obsen'ed, which has the same absorption profile in both cases. Our work on lhin-film samples shows lhal th$ excitation causing this absorption is polarized in the ab plane. Funher work on doped powder samples provides evidence lhat the excitation is localized in the CuO2 planes of the slruclure. which are known 10

Phonon softening and MIR absorption in superconducting

“…We now turn to the discussion of the MIR absorption which has previously been observed in other oxide superconductors [24][25][26][27][28][29] and was considered as one of the strongest indications for the existence of polarons in high-temperature superconductors [24,26]. The MIR absorption coefficient in YBCO and LSCO changes from a strong temperature dependence at T > T c to an almost temperature-independent behaviour at T < T c .…”