Persistent and transient photoconductivity in oxygen-deficient La_2/3Sr_1/3MnO_3-δ thin films

Light illumination produces major, interesting changes of the electrical properties of oxygen deficient La_2/3Sr_1/3MnO_3-δ thin films. At small oxygen deficiency, the classical insulator-metal (I-M) transition at a temperature T_p decreases with increasing oxygen deficiency. The low-temperature metallic behavior in darkness shows a persistent increase of the conductivity with light. This photoconductivity increases with oxygen deficiency (from a few to 60%). At large, oxygen deficiency, the films are semiconducting in darkness, from helium to room temperature and light induces a transient photoconductivity and a low-temperature I-M transition. The intriguing possibility of collective light induced magnetism is discussed.