Temperature effects in the optical absorption of superconducting YBa2Cu3O7–<i>δ</i> films
I. Ya. Fugol’Physicotechnical Institute of Low Temperatures, Academy of Sciences of the Ukrainian SSR, KharkovV. N. SamovarovPhysicotechnical Institute of Low Temperatures, Academy of Sciences of the Ukrainian SSR, KharkovYu. I. RybalkoPhysicotechnical Institute of Low Temperatures, Academy of Sciences of the Ukrainian SSR, KharkovV. M. ZhuravlevPhysicotechnical Institute of Low Temperatures, Academy of Sciences of the Ukrainian SSR, Kharkov
ABI
Abstract
Experimental studies of the temperature dependence of several superconducting films of YBa2Cu3O7–δ have been carried out in the energy interval 1.5–3 eV at temperatures between 25 and 300 K. The spectra are found to be sensitive to the superconducting transition, and an exciton peak at 1.95 eV which is associated with a transition from the states near the Fermi level, is singled out at low temperatures. The freezing of the absorption spectrum at T &lt; Tc is attributed to the emergence of a temperature resonance of the Fermi level with a narrow local level corresponding to a delta-shaped peculiarity in the density of states.
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