Photoinduced changes in the absorption spectrum of superconducting YBa2Cu3O7–<i>δ</i> films in the 1.5–3 eV region
I. Ya. Fugol’B. I. Verkin Physicotechnical Institute of Low Temperatures, 310164, Khar’kov, pr. Lenin, 47V. N. SamovarovB. I. Verkin Physicotechnical Institute of Low Temperatures, 310164, Khar’kov, pr. Lenin, 47Yu. I. RybalkoB. I. Verkin Physicotechnical Institute of Low Temperatures, 310164, Khar’kov, pr. Lenin, 47V. M. ZhuravlevB. I. Verkin Physicotechnical Institute of Low Temperatures, 310164, Khar’kov, pr. Lenin, 47G. Zaimann-lshchenkoPhysics Institute, Erlangen University, GermanyB. Khol’tsapfelPhysics Institute, Erlangen University, GermanyI. Shtrebel’Siemens Corp., Erlangen, Germany
ABI
Abstract
We have studied experimentally the absorption spectrum of crystalline superconducting films of YBa2Cu3O7–δ in the energy region 1.5–3 eV, for temperatures from 300 to 20 K. Magnetic characterization of the films using a SQUID magnetometer revealed the presence of two superconducting phases with critical temperatures 87.5 and ∝ 50 K. We find that the absorption spectrum is sensitive to both superconducting transitions. For the low temperature phase with Tc = 50 K, we observe long-lived photoinduced changes in the absorption spectrum (photochromic effect). We discuss the band structure of the electronic transitions responsible for the absorption spectrum and the photoinduced changes.
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