We have successfully obtained asymmetrical current–voltage (I–V) characteristics in YBa2Cu3O7-x (YBCO) nanobridges patterned with asymmetrical geometry. These asymmetrical nanobridges (ANBs) are shown to control vortices one at a time. The critical current I c, of 200-nm-wide and 100-nm-thick ANB changes by a maximum of 9% when a magnetic field of 2.4 mT is applied. The I c variation ΔI c increases monotonically with increased magnetic field from -2.2 to 2.4 mT. The asymmetrical I–V characteristics obtained in our experiment are due to the restriction of vortex motion by the asymmetrical surface barrier (the so-called vortex ratchet effect). The width and thickness dependencies of the I–V asymmetry are also studied, and indicate that the bias current and the Meissner screening current, determined by the relative width compared to the effective penetration depth of the YBCO film, dominates the I–V asymmetry characteristics.

No abstract

No abstract

No abstract