Nano-fabrication tool for vortex manipulation in YBCO superconductors

R. F. LUCCAS; A. PALAU; X. GRANADOS; T. PUIG; X. OBRADORS

Madrid

Congreso; Third Spanish Workshop on Nanolithography; 2009

IMM-CNM

YBCO is a superconducting material with a broad field of applications which properties are determined by vortex pinning and vortex dynamics. Natural defects like twin boundaries, stacking faults, dislocations, secondary phases,... may act as vortex pinning centers. However, one desires to introduce artificial defects in a controlled manner to tune the superconducting properties. In this work we use two different nano-fabrication techniques (irradiation with focused ion beam and indentations at nano-scale) as tools to generate artificial defects. We have studied the interaction between vortices and the linear arrays of artificial nano-defect by direct observation of the vortex lattice using the Bitter decoration technique. We demonstrate that such artificial defects localize individual vortices and modify the pre-existing order/disorder and symmetry of the vortex lattice. Furthermore, Bitter decoration images have been used to evaluate and quantify the vortex pinning capabilities of each generated artificial defect array and the total energy of the vortex lattice. A model has been developed for this purpose based on London theory as an approximation of the Ginzburg-Landau solution, with a general analytic expression for the energy of arbitrary arrangements of vortex position[1]. We observe that pinning energy increases (decreases) in agreement with the increase of the order (disorder) in the system. Fig. 1. Bitter decoration performed in an YBCO sample with linear defects artificially generated by nanoindentation (a) and the corresponding interaction energy map for vortex positions (b). Artificial defects vertically disposed at the left half of the image manipulate vortices imposing them a linear correlation and also increasing their interaction energy. [1] E.H. Brandt, Supercond. Sci. Technol., 22, 034019 (2009).