Visualization of novel flux dynamics in YBa2Cu3O7-x thin films with antidots

Using magneto-optical visualization, individual 2 mum diameter antidots ( c ircular holes) in YBa2Cu3O7-x thin films are clearly observed. These antido ts are found to act at low temperature as very strong pinning centres. Flux penetration takes place along the lattice vectors of the antidot lattice. Both commensurate and incommensurate channels are observed as well as hoppi ng between channels, in agreement with numerical simulations. Surprisingly, even for these large (r/lambda similar or equal to7) antidots the trapped flux is in agreement with previous theoretical work for small (r << lambda) antidots.