Persistent photoconductivity in insulating and superconducting ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathit{x}}$ thin films: Temperature and spectral dependence

Temperature and spectral dependencies of photoinduced changes of resistance in ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{\mathit{x}}$ thin films with oxygen content ranging as 6.35<x<6.75 were measured on both sides of the metal-insulator transition (MIT). The absolute value of efficiency of initiation of photoinduced changes decreases with an increase of oxygen content, but the position of peaks in the spectral dependence does not change with a change of x. Temperature dependencies of efficiency have an anomaly at T∼220 K, which is present in all the samples studied and correlates with anomalies observed by other experimental techniques. Qualitatively similar temperature and spectral dependencies of efficiency for the samples in both the insulating and metallic phases may be considered as an indication that the persistent photoconductivity effect in Y-Ba-Cu-O on both sides of the MIT has a common origin.