Flux Flow of Josephson Vortices in La2-xSrxCuO4 Single Crystals

We observed a sharp up-tum in the current-voltage (I-V) characteristics of the intrinsic Josephson junctions fabricated from a La2-xSrxCuO4 single crystal in a magnetic field applied parallel to the ab plane. The I-V curves show a up-tum behavior with increasing the field, and become vertical for higher fields. We can explain that this up-tum is caused by matching between the velocity of Josephson vortices and the mode velocity of electromagnetic waves whose mode numbers depend on the field strength.