Photoexcitation and oxygen ordering in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">YBa</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>films

We report on the photoinduced enhancement of the critical temperature \ensuremath{\delta}${\mathit{T}}_{\mathit{c}}$ and the in-plane conductivity \ensuremath{\delta}${\mathrm{\ensuremath{\sigma}}}_{\mathit{a}\mathit{b}}$ measured in a c-axis-oriented ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{x}}$ film as a function of oxygen concentration (6.4\ensuremath{\le}x\ensuremath{\le}7). Both \ensuremath{\delta}${\mathit{T}}_{\mathit{c}}$ and \ensuremath{\delta}${\mathrm{\ensuremath{\sigma}}}_{\mathit{a}\mathit{b}}$ decrease with the oxygen content, display a plateaulike behavior for 6.6\ensuremath{\le}x\ensuremath{\le}6.75, and become zero at x=7. This dependence of \ensuremath{\delta}${\mathit{T}}_{\mathit{c}}$ on x is similar to that observed for the ${\mathit{T}}_{\mathit{c}}$ enhancement due to ordering effects in oxygen-deficient ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{x}}$ single crystals. We propose that the persistent photoinduced changes in ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{x}}$ films are due to photoassisted oxygen ordering.

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